Exchange system for soft tissue access pathway

ABSTRACT

Disclosed are surgical tools, tool sets and methods for percutaneously accessing and preparing treatment sites within the spine for subsequent treatment procedures. The treatment site may be an inter-vertebral motion segments in the lumbar and sacral regions of the spine. The tool set may comprise introducer tools and bone dilators for accessing and tapping into a targeted site, such as, for example, the anterior surface of the S1 vertebral body. The tool set may also comprise cutters and extractors for preparing the treatment site for subsequent treatment procedures. The tool set may additionally comprise a bone graft inserter, an exchange system, and/or a temporary distraction tool for further preparing the treatment site for subsequent treatment procedures.

RELATED APPLICATIONS

This U.S. Patent Application claims priority and benefits from U.S.Provisional Patent Application No. 60/513,899, filed on Oct. 23, 2003,and co-pending U.S. patent application Ser. No. 10/309,416, filed onDec. 3, 2002, which is a continuation-in-part of U.S. patent applicationSer. No. 10/125,771, filed on Apr. 18, 2002, which is acontinuation-in-part of U.S. patent application Ser. No. 09/848,556,filed on May 3, 2001, which is a continuation-in-part of U.S. patentapplication Ser. No. 09/782,583, filed on Feb. 13, 2001, which claimspriority to U.S. Provisional Patent Application No. 60/182,748, filed onFeb. 16, 2000. This U.S. Patent Application also claims priority andbenefits from co-pending U.S. patent application Ser. No. 10/853,476,filed May 25, 2004, which is a continuation of U.S. patent applicationSer. No. 09/710,369, filed on Nov. 10, 2000. This U.S. PatentApplication also claims priority and benefits from co-pending U.S.patent application Ser. No. 09/782,534, filed on Feb. 13, 2001, andco-pending U.S. patent application Ser. No. 10/459,149, filed on Jun.10, 2003, both of which claim priority to U.S. Provisional PatentApplication No. 60/182,748, filed Feb. 16, 2000. The contents of each ofthe aforementioned U.S. Patent Applications are hereby incorporated intheir entirety into this disclosure by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to instrumentation systems andmethods for accessing and preparing treatment sites within the spine(e.g., inter-vertebral motion segments) for subsequent therapeuticprocedures, such as, for example, spinal arthroplasty, partial or totaldisc replacement, annulus repair, vertebroplasty, arthrodesis (fusion),or the like. Disclosed herein are various tools and methods of use(e.g., surgical cutting devices, tissue extractors, etc.) for performingany number of minimally-invasive treatment procedures (e.g., low traumadisc nucleectomy via trans-sacral axial access). The methods caninvolve, among other things, facilitating the removal of resultingtissue fragments, preparing an intervertebral disc space for subsequentdeployment of spinal fusion designed to relieve lower back pain, ormotion preservation devices, e.g., dynamic stabilization, devices,prosthetic nucleus devices and total disc replacements designed torelieve lower back pain and to restore physiological function of thelumbar spine, maintain and possibly improve disc health and preventprogression or transition of disease.

2. Description of the Related Art

Chronic lower back pain is a primary cause of lost work days in theUnited States, and as such is a significant factor affecting bothworkforce productivity and health care expense. Therapeutic proceduresfor alleviating back pain range from conservative methods, e.g., withintermittent heat, rest, rehabilitative exercises, and medications torelieve pain, muscle spasm, and inflammation, to progressively moreactive and invasive surgical means which may be indicated if thesetreatments are unsuccessful, including various spinal arthroplasties,and eventually even spinal arthrodesis, i.e., surgical fusion.

There are currently over 700,000 surgical procedures performed annuallyto treat lower back pain in the U.S. In 2004, it is conservativelyestimated that there will be more than 200,000 lumbar fusions performedin the U.S., and more than 300,000 worldwide, representing approximatelya $1B endeavor in an attempt to alleviate patients' pain. In addition,statistics show that only about 70% of these procedures performed willbe successful in achieving this end.

Moreover, there may be multiple causes for a patient's lower back pain,where the pain generators are hypothesized to comprise one or more ofthe following: bulging of the posterior annulus or PLL with subsequentnerve impingement; tears, fissures or cracks in the outer, innervatedlayers of the annulus; motion induced leakage of nuclear materialthrough the annulus and subsequent irritation of surrounding tissue inresponse to the foreign body reaction, or facet pain. Generally it isbelieved that 75% of cases are associated with degenerative discdisease, where the intervertebral disc of the spine suffers reducedmechanical functionality due to dehydration of the nucleus pulposus.

The intervertebral discs, located anterior to the vertebral canal, areformed of fibrous cartilage, and comprise the posterior and anteriorlongitudinal ligaments and the annulus fibrosis, circumferentiallyenclosing a central mass, the. The nucleus pulposus provides forcushioning and dampening of compressive forces to the spinal column. Ina healthy adult spine, it comprises 80% water.

Surgical procedures, such as spinal fusion and discectomy, may alleviatepain, but do not restore normal physiological disc function.

With reference to FIGS. 1A and 1B, the vertebrae are the bony buildingblocks of the spine. Between each of the vertebral bodies are the spinaldiscs and this unit, comprising two vertebral bodies interfaced by anintermediate spinal disc, is known as a spinal motion segment. The spinehas seven vertebrae in the neck (cervical vertebrae), twelve vertebraein the mid-back (thoracic vertebrae), and five vertebrae in the low back(lumbar vertebrae). All of the vertebrae and discs are held together orsurrounded by means of ligaments, which are strong fibrous soft tissuesthat firmly attach bones to bones. Ligaments contribute to the normalphysiologic range of motion of the spine, and if injured, e.g., due todisc degeneration (described below) and ensuing impact on distributionof physiologic loads, they similarly may contribute to the resultingpain.

Thus, the bony spine is designed so that vertebrae “stacked” togethercan provide a movable support structure while also protecting the spinalcord's nervous tissue that extends down the spinal column from the brainfrom injury. Each vertebra has a spinous process, which is a bonyprominence behind the spinal cord that shields the cord's nerve tissue.The vertebrae also have a strong bony “body” in front of the spinal cordto provide a platform suitable for weight-bearing.

The spinal discs serve as “dampeners” between each vertebral body thatminimize the impact of movement on the spinal column. Each disc iscomprised of the nucleus pulposus, a central, softer component,contained with in the, a surrounding outer ring.

With age, the water and protein content of the body's cartilage changesresulting in thinner, more fragile cartilage. Hence, the spinal discsand the facet joints that stack the vertebrae, both of which are partlycomposed of cartilage, are subject to similar degradation over time. Thegradual deterioration of the disc between the vertebrae is known asdegenerative disc disease, or spondylosis. Spondylosis is depicted onx-ray tests or MRI scanning of the spine as a narrowing of the normal“disc space” between adjacent vertebrae.

Radiculopathy refers to nerve irritation caused by damage to the discbetween the vertebrae. This occurs because of degeneration of theannulus fibrosis of the disc, or due to traumatic injury, or both.Weakening of the annulus may lead to disc bulging and herniation, i.e.,the nucleus pulposus or softer portion of the disc can rupture throughthe annulus and abut the spinal cord or its nerves as they exit the bonyspinal column. When disc herniation occurs, the rupture of the nucleuspulposus the annulus fibrosis may irritate adjacent nervous tissue,causing local pain, or discogenic pain, in the affected area. Any levelof the spine can be affected by disc degeneration. When discdegeneration affects the spine of the neck, it is referred to ascervical disc disease, while when the mid-back is affected, thecondition is referred to as thoracic disc disease. Disc degenerationthat affects the lumbar spine causes pain localized to the low back andis sometimes common in older persons and known as lumbago Degenerativearthritis (osteoarthritis) of the facet joints is also a cause oflocalized lumbar pain that can be diagnosed via x-ray analysis.

The pain from degenerative disc or joint disease of the spine may betreated conservatively with intermittent heat, rest, rehabilitativeexercises, and medications to relieve pain, muscle spasm, andinflammation, but if these treatments are unsuccessful, progressivelymore active interventions may be indicated, including spinalarthroplasty including prosthetic nucleus device implantation; annulusrepair, and total disc replacement, and eventually, even spinalarthrodesis, The intervention performed depends on the overall status ofthe spine, and the age and health of the patient. Procedures includeremoval of the herniated disc with laminotomy (a small hole in the boneof the spine surrounding the spinal cord), laminectomy (removal of thebony wall), by needle technique through the skin (percutaneousdiscectomy), disc-dissolving procedures (chemonucleolysis), and others.

When narrowing of the spaces in the spine results in compression of thenerve roots or spinal cord by bony spurs or soft tissues, such as discs,in the spinal canal this condition is known as spinal stenosis. Spinalstenosis occurs most often in the lumbar spine, i.e., the lower back,but also occurs in the cervical spine and less often in the thoracicspine. It is most often caused by degeneration of the discs between thevertebrae due to osteoarthritis. Rheumatoid arthritis usually affectspeople at an earlier age than osteoarthritis does and is associated withinflammation and enlargement of the soft tissues of the joints. Theportions of the vertebral column with the greatest mobility, i.e., thecervical spine, are often the ones most affected in people withrheumatoid arthritis. Non-arthritic causes of spinal stenosis includetumors of the spine, trauma, Paget's disease of bone, and fluorosis.

In the context of the present invention, therapeutic procedures toalleviate pain are restore function are described in a progression oftreatment from spinal arthroplasty to spinal arthrodesis. As usedherein, spinal arthroplasty encompasses options for treating discdegeneration when arthrodesis is deemed too radical an interventionbased on an assessment of the patient's age, degree of discdegeneration, and prognosis.

A wide variety of efforts have been proposed or attempted in the priorart, in an effort to relieve back pain and restore physiologicalfunction. Notwithstanding these efforts, there remains a need formethods and tools for accessing and preparing an intervertebral motionsegment for subsequent therapeutic procedures, which can be accomplishedin a minimally invasive manner.

SUMMARY OF THE INVENTION

The preferred embodiments of the invention involve surgical tools setsand methods for accessing and preparing vertebral elements, such asinter-vertebral motion segments located within a human lumbar and sacralspine, for therapeutic procedures. In the context of the presentinvention, “motion segments” comprise adjacent vertebrae separated byintact or damaged spinal discs.

In particular embodiments of the present invention, instrumentationsystem components and their means of use, individually and incombination and over or through one another, form or enlarge a posterioror anterior percutaneous tract; access, fragment and extract tissue(e.g., nucleus pulposus,); or otherwise prepare vertebral elements andinter-vertebral motion segments for fusion or dynamic stabilization viaimplantation of therapeutic agents and materials and spinal devices, aredisclosed. It will be noted that the tools described can be used for andwith the introduction of any number of devices, such as, for example,fusion devices, mobility devices, etc. Instrumentation is introduced andaligned (e.g., via preferably fluoroscopy, endoscopy, or otherradio-imaging means, used as guidance to insure that the channel ispositioned mid-line or along another desired reference axis relative tothe anterior/posterior and lateral sacral view) through the percutaneouspathways and according to the trans-sacral axial access methodsdisclosed by Cragg, in commonly assigned U.S. Pat. Nos. 6,558,386,6,558,390, and 6,575,979, each incorporated herein in their entirely byreference.

In another aspect, the present invention provides a series of surgicaltools and devices, wherein the preferred embodiments of each areconfigured and constructed (e.g., cannulated; solid; blunt; beveled;angled; retractable; fixed; tilted; axially aligned; offset; extendible;exchangeable; stiff; flexible; deformable; recoverable; anchored;removable; biocompatible; able to be sterilized & machined; moldable;reusable; disposable) in accordance with optimal intended function andin deference to biomechanical and safety constraints.

Certain of the surgical tools take the form of elongated solid bodymembers extending from proximal to distal ends thereof. Such solid bodymembers may be used in combination or sequentially with elongated,cannulated body members. Hence, for example, design constraints, inaddition to outside diameter (O.D.) tolerances and limitations imposedby virtue of patient anatomies, such as tube wall thickness, materialselection/mechanical strength, and inside diameter (I.D.) also becomeconsiderations, e.g., to enable unrestricted passage over guide membersor through hollow body members without incurring deformation that mayimpair or otherwise preclude intended function. Certain of these solidbody and hollow body members can have distal means, mechanisms, orapertures that may be configured or manipulated for either precluding orfacilitating engagement with tissue; the latter including piercing;tapping; dilating; excising; fragmenting; extracting; drilling;distracting (e.g. elevating); repairing; restoring; augmenting; tamping;anchoring; stabilizing; fixing, or fusing tissue. Certain of these solidbody and hollow body members can have proximal means, mechanisms, pins,slots or apertures that may be configured or manipulated to engage;grasp; twist; pilot; angle; align; extend; expose, retract; drive;attach or otherwise interact to enable or facilitate the functionalityof other components within the surgical tools set, e.g., the distalmeans and mechanisms noted above in this paragraph. In accordance withthe certain embodiments disclosed herein, the individual componentscomprised in the tools sets, or kits, may include a guide pinintroducer; guide pins with various distal end and proximal endconfigurations (e.g., tips; handles, respectively); soft tissue and bonedilators and dilator sheath(s); cutters; tissue extraction tools; twistdrills; exchange systems comprising exchange bushing and exchangecannula assemblies; distraction tools; augmentation materials, andrepair tools.

In a particularly preferred procedure, these instrumentation systemcomponents are aligned axially, under visualization, and progressivelyinserted into a human lumbar-sacral spine through the minimally invasivepercutaneous entry site adjacent the coccyx to access the L5-S1 or L4-L5disc space to perform a partial or total nucleectomy, withoutcompromising the annulus fibrosis, unlike current surgical discectomyprocedures. Conventional discectomies are performed through a surgicallycreated or enlarged hole in the annulus that remains post-operatively,and represents a undesirable pathway due to the potential for extrusionand migration of natural or augmented tissue, or implants, and that alsocompromise the biomechanics of the physiological disc structure.

Moreover, in accordance with the techniques and surgical tool sets, andin particular the cutters and extraction tool configurations disclosedherein, a substantially greater amount (volume) of intradiscal materiale.g., nucleus pulposus and cartilage, in comparison with otherdiscectomy procedures in practice, may be removed, as needed. Inparticular, the instrumentation systems and techniques embodied in thepresent invention more effectively, with less immediate trauma, andwithout residual negative physiological impacts that may occur as aresult of invasion of the annulus, prepare an inter-vertebral motionsegment for subsequent receipt of therapeutic procedures, and enablesaxial placement of implants close to and in alignment with the humanspine's physiological center of rotation.

Other specific advantages over current practice include: the patient isin a prone position that is easily adaptable to other posteriorinstrumentation; blood loss is minimal soft tissue structures, e.g.,veins, arteries, nerves are preserved, and substantially less surgicaland anesthesia time are required compared with conventional procedures.

There is provided in accordance with one aspect of the presentinvention, an exchange system for increasing the cross-sectional area ofan access pathway through soft tissue to a surface of a bone. Theexchange system comprises an elongate tubular exchange bushing having aproximal end, a distal end, and a central lumen extending therethrough.An elongate tubular exchange cannula having a proximal end, a distalend, and a central lumen extending therethrough is also provided, theexchange cannula comprising a beveled distal end. The exchange bushingis axially slidable within the central lumen of the exchange cannula.

The bevel may be at an angle within the range of from about 20 degreesto about 70 degrees with respect to a longitudinal axis of the exchangecannula. In certain embodiments, the bevel is within the range of fromabout 30 degrees to about 60 degrees with respect to the longitudinalaxis. A handle may be provided on the proximal end of the exchangecannula.

The exchange system may additionally comprise an indicium of therotational orientation of the bevel. The indicium may comprise a visiblemarker, such as a dot, line or groove, on the proximal end of theexchange cannula. In one implementation, the indicium comprises at leastone notch on an annular band carried by the proximal end of the exchangecannula.

The exchange system may additionally comprise a plurality of distallyextending fingers on the distal end of the exchange cannula, the fingersmovable between a first, reduced outside diameter configuration and asecond, enlarged outside diameter configuration. The exchange bushingmay comprise a recess for receiving the fingers when in the first,reduced outside diameter configuration.

In accordance with a further aspect of the present invention, there isprovided a method of advancing a device along an access tract. Themethod comprises the steps of positioning a dilator sheath between anaccess site and a target site on a bone. A tubular exchange bushing isadvanced over the dilator sheath. A tubular exchange cannula is advancedover the exchange bushing. The dilator sheath and the exchange bushingare removed, leaving the exchange cannula in position along the accesstract. The device is introduced through the exchange cannula.

The device may be an implant, such as a spinal fusion implant, a spinalmotion preservation implant, or a site preparation tool. The device mayhave a cross-sectional area that is greater than the insidecross-sectional area of the dilator sheath.

The target site may be on the sacrum. The introducing the device stepmay comprise enlarging the diameter of at least a portion of theexchange cannula. The method may additionally comprise radiallyenlarging a distal tapered portion of the exchange cannula. The accesstract may have a longitudinal axis which intersects the surface of thebone at an angle, and the distal end of the exchange cannula is beveledat an angle that corresponds to the angle at which the axis intersectsthe surface of the bone.

These and other advantages and features of the surgical tools sets andtechniques disclosed in the present invention will be more readilyunderstood from the following detailed description of the preferredembodiments thereof, when considered in conjunction with theaccompanying figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A provides a lateral view of a normal spinal column.

FIG. 1B illustrates examples of normal, degenerated, bulging, herniated,and thinning spinal discs.

FIG. 1C is a lateral view of the lumbar and sacral portion of the spinalcolumn depicting the visualized anterior axial instrumentation/implantline (AAIIL) extending cephalad and axially from the anteriorlaminectomy site target point.

FIG. 1D is an illustration of an anterior target point on the sacrrum

FIGS. 1E and 1F are cross-sectional caudal views of a lumbar vertebraedepicting one and two trans sacral axial implants respectively withincorresponding TASII bores formed in parallel with the visualized AAIILof FIG. 1C.

FIGS. 2A and 2B are a perspective view and a side cross-sectional viewof one embodiment of a guide pin introducer, respectively, with pin andslot configuration.

FIG. 2C is a side cross-sectional view of one embodiment of a styletwith pin configuration.

FIG. 2D is a perspective view of one embodiment of a guide pinintroducer-stylet-pin and slot configured assembly.

FIG. 2E is a side cross-sectional view of the assembly of FIG. 2D.

FIG. 3A is a perspective view of one embodiment of a guide pinintroducer.

FIG. 3B is a side cross-sectional view of the guide pin introducer ofFIG. 3A.

FIG. 3C is a side cross-sectional view of one embodiment of a styletwith multi-start thread configuration.

FIG. 3D is a perspective view of one embodiment of a guide pinintroducer-stylet multi-start thread configured assembly.

FIG. 3E is a side cross-sectional view of the assembly of FIG. 3D.

FIGS. 4 and 5 are lateral, partial cross-sectional views of the lumbarand sacral portion of the spine depicting delivery of the distal end ofguide pin introducer-stylet-assembly to the anterior surface of the S1vertebral body.

FIG. 6A is a side view of a guide pin detailing distal and proximalends.

FIG. 6B is a side view of the distal end of one embodiment of a guidepin with a trocar tip configuration.

FIG. 6C is a side view of the distal end of an embodiment of a guide pinwith a beveled tip configuration.

FIG. 6D is a side view of the proximal end of a preferred embodiment ofa guide pin with a hex and flat configuration as means for tip alignmentand axial and rotational locking.

FIG. 7A is a cross sectional view of a guide pin-guide pin handleassembly.

FIG. 7B is a cross sectional view of a guide pin handle.

FIG. 7C depicts the thumb screw, for locking the guide pin.

FIG. 7D illustrates a means for guide pin stop and steering.

FIG. 7E depicts a guide pin assembly inserted within an introducerillustrating the guide pin tip extending beyond the distal end of theintroducer.

FIG. 7F is a cross section view illustrating a guide pin handleassembly, showing a releasable engagement means with the guide pin.

FIG. 8A illustrates a guide pin-guide pin extension assembly with athreaded engagement coupling.

FIG. 8B is a detailed view of guide pin-guide pin extension assemblywith a threaded engagement coupling.

FIG. 8C illustrates a guide pin with a cross-sectional view of femalethread engagement coupling.

FIG. 8D is an enlarged view of the female thread engagement coupling inFIG. 8C.

FIG. 8E illustrates the guide pin extension with a cross-sectional viewof a male thread engagement coupling.

FIG. 8F is an enlarged view of the male thread engagement in FIG. 8E.

FIG. 8G illustrates an alternative embodiment of a guide pin-guide pinextension assembly with a friction fit engagement coupling.

FIG. 9 is a side view of a slap hammer and a dilator handle on anextended guide pin.

FIG. 10 is an elevated view of three differently sized dilators.

FIG. 11 is a perspective view of one embodiment of a dilator.

FIG. 12 is a side cross-sectional view of the distal portion of thedilator in FIG. 11.

FIG. 13A is a perspective view of one embodiment of a large dilator witha dilator sheath.

FIG. 13B is a side cross-sectional view of a distal portion of the largedilator within the dilator sheath of FIG. 13A.

FIG. 13C is a perspective view of the sheath of the large dilator ofFIG. 13A.

FIG. 13D is a perspective view of another embodiment of a large dilatorsheath.

FIG. 14 is a side view of one embodiment of a twist drill.

FIG. 15 shows a cutter extending through a dilator sheath (dockingcannula) in the L5-S1 disc space.

FIG. 16A is a perspective view of one embodiment of a cutter assemblythat comprises a down-cutter.

FIG. 16B is a side cross-sectional view of the cutter assembly of FIG.16A.

FIG. 16C is an exploded, perspective view of the distal portion of thecutter assembly of FIG. 16A.

FIGS. 16D and 16E are elevated views of one embodiment of a smalldown-cutter.

FIG. 16F is a cross sectional view of a proximal cutter blade arm (402′)for nucleectomy prior to a mobility preservation procedure taken alongthe line 16F-16F in FIG. 16E.

FIG. 16G is a cross sectional view of a proximal cutter blade arm (402′)for nucleectomy prior to a fusion procedure taken along the line 16F-16Fin FIG. 16E. The inclined plane (421) is a mirror image of that in ofFIG. 16F.

FIG. 16H illustrates one embodiment of an upcutter (452).

FIG. 161 is a cross sectional view of a distal sleeve-shaftconfiguration showing a retraction stop mechanism for both a tissuecutter.

FIG. 17A is an exploded, perspective view of the distal portion of acutter assembly that comprises a debulker.

FIGS. 17B-17C are elevated views of the debulker of the cutter assemblyof FIG. 17A.

FIGS. 17D-17E are elevated views of one embodiment of a large debulker.

FIG. 18A is an elevated view of one embodiment of a large teardropdebulker.

FIG. 18B is a rear elevational view of the portion teardrop debulker ofFIG. 18A which attaches to the rotatable shaft.

FIG. 18C is another elevated view of a larger teardrop debulker of FIG.18A.

FIG. 18D is an elevated view of one embodiment of a standard or mediumsize teardrop debulker.

FIG. 18E is a side isometric view of one embodiment of a large teardropdown-cutter.

FIG. 18F is a side isometric view of one embodiment of a medium teardropdown-cutter.

FIG. 18G is a side isometric view of one embodiment of a small teardropdown-cutter.

FIG. 19A is a side elevated perspective view of one embodiment of anextractor assembly unit.

FIG. 19B is a side elevated, partial cut-away view of the extractorassembly unit of FIG. 19A.

FIG. 19C is a side cross-sectional view of the extractor assembly unitof FIG. 19A.

FIG. 19D is a side elevated view of an extractor head prior to havingits component wires unwound.

FIG. 20 illustrates the distal end of one embodiment of an extractiontool with tissue fragments within its wire strands.

FIGS. 21A-B illustrate one embodiment of an extractor tool with its headextended into an exposed position and then pulled back into a deliverysleeve.

FIGS. 21C-D illustrate another embodiment of an extractor tool with itshead in the extended position.

FIGS. 22A-B illustrate another embodiment of an extraction tool.

FIG. 23A is a perspective view of one embodiment of an insertion toolassembly comprising a packing instrument and a delivery cannula.

FIG. 23B illustrates engagement of the packing instrument with thedelivery cannula, both from FIG. 23A.

FIG. 23C is perspective view of the packing instrument of FIG. 23A.

FIG. 23D is a perspective view of the delivery cannula of FIG. 23A.

FIG. 24A is a perspective view of one embodiment of a paste-inserterassembly.

FIG. 24B is a side cross-sectional view the assembly of FIG. 24A.

FIG. 25A is a perspective view of one embodiment of an allograftplacement tool.

FIG. 25B is a side cross-sectional view of the tool of FIG. 25A.

FIG. 25C is a side cross-sectional view of the allograft tip of the toolof FIG. 25A.

FIG. 26 is a side elevated view of an exchange bushing.

FIG. 27 is a side view of one embodiment of an exchange system assemblycomprising an exchange bushing and an exchange cannula.

FIG. 28A is a side elevated, cut-away view of one embodiment of anexchange cannula of FIG. 27, in an open configuration.

FIG. 28B is a side elevated view of the exchange cannula of FIG. 27, ina closed configuration.

FIGS. 29A-B illustrate the use of the exchange system of FIGS. 26-28 todeliver a distraction device or an axial spinal implant of largerdiameter than the dilater sheath.

FIG. 30A is side cross-sectional view of another embodiment of anexchange system assembly comprising an exchange bushing and an exchangetube.

FIG. 30B is a side cross-sectional view of the exchange bushing of FIG.30A.

FIG. 30C is a side cross-sectional view of the exchange tube of FIG.30A.

FIG. 30D is a perspective view of another embodiment of an exchangesystem comprising an exchange bushing and an exchange tube.

FIG. 30E is a bottom perspective view of the exchange system of FIG.30D.

FIG. 31 is a perspective view of one embodiment of a temporarydistraction rod and a tool that can be used to deliver or remove the rodfrom a treatment site.

FIG. 32A is a perspective, partial cut-away view of the temporarydistraction rod of FIG. 32A and the distal portion of a tool that can beused to deliver the rod to the treatment site.

FIG. 32B is a perspective, partial cut-away view of the temporarydistraction rod of FIG. 32A and the distal portion of a tool that can beused to remove the rod from the treatment site.

FIG. 33A is a perspective, partial cut-away view of the distal portionof one embodiment of a temporary distraction rod.

FIG. 33B is a side cross-sectional view of the rod distal portion ofFIG. 33A.

FIG. 33C is a perspective view of the proximal portion of one embodimentof a temporary distraction rod.

FIG. 33D is another perspective view of the rod proximal portion of FIG.33C.

FIG. 33E is a side cross-sectional view of the rod proximal portion ofFIG. 33C.

FIG. 34A is an exploded perspective view of one embodiment of adistraction-rod-assembly shown with the insertion tool.

FIG. 34B is a perspective view of the insertion tip of the assembly ofFIG. 34A.

FIG. 34C is another perspective view of the insertion tip of theassembly of FIG. 34A.

FIG. 35A is a perspective, exploded view of one embodiment of atemporary distraction-rod-assembly, shown with the removal tool.

FIG. 35B is a front perspective view of the tip of the removal toolassembly of FIG. 35A.

FIG. 35C is a rear perspective view of the tip of the removal toolassembly of FIG. 35A.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In accordance with one aspect of the embodiments described herein, thereare provided surgical instrumentation systems and techniques forefficiently and atraumatically accessing and preparing treatment siteswithin the spine, such as, for example, vertebral motion segments, forsubsequent therapeutic spinal procedures. In one approach, the step ofaccessing the treatment site includes using fluoroscopic imaging tovisually align one or more components of the instrumentation system viaa percutaneous, anterior trans-sacral axial approach. In another aspect,the treatment site includes a spinal disc and the subsequent therapeuticprocedure includes nucleectomy. In yet another aspect, the therapeuticprocedure includes immobilization devices to facilitate fusion;deployment of augmentation media; deployment of dynamic stabilizationimplants, or mobility devices to preserve or restore physiologicfunction.

In accordance with one aspect of the embodiments described herein, thereare provided surgical tool sets and methods of using the tool sets. Thetools of the tools sets can be used individually and/or in combinationwith each other. As will be explained in further detail below, in oneapproach, certain tools fit over other tools, and therefore can be usedover each other. In another approach, the tools fit through each other,and therefore can be used through one another.

It will be understood that the access methods described can include thestep of utilizing an anterior or posterior trans-sacral pathway. Thetherapies to the spinal discs and vertebral bodies described herein canbe conducted on one or more spinal discs or vertebral bodies. In oneapproach, therapeutic procedures are performed through or on at leastone spinal disc and at least one vertebral body traversed by at leastone working channel.

For convenience, the exemplary access by a single anterior method, andtreatment of only a single spinal disc or vertebral body is describedherein. It will be understood, however, that the tools and methodologiesdescribed herein are applicable to any spinal access pathway, includingwithout limitation open surgical procedures from any access orientation,and to any number of spinal discs and/or vertebral bodies.

FIGS. 1C-D schematically illustrate the anterior trans-sacral axialspinal instrumentation/implant (TASII) approaches in relation to thelumbar region of the spinal column, and FIGS. 1E-F illustrate thelocation of a TASII implant or pair of implants within an anterior TASIIaxial bore 152 or pair of TASII axial bores 22 ₁, 22 ₂, or 152 ₁, 152 ₂.Two TASII axial bores and spinal implants or rods are shown in FIG. 1Fto illustrate that a plurality, that is two or more, of the same may beformed and/or employed in side by side relation parallel with theanterior axial instrumentation/implant line (AAIIL).

The lower regions of the spinal column comprising the coccyx, fusedsacral vertebrae S1-S5 forming the sacrum, and the lumbar vertebraeL1-L5 described above are depicted in a lateral view in FIG. 1C. Theseries of adjacent vertebrae located within the human lumbar and sacralspine have an anterior aspect, a posterior aspect and an axial aspect,and the lumbar vertebrae are separated by intact or damaged spinal discslabeled D1-D5 in FIG. 1C. FIG. 1D depicts the anterior view of thesacrum and coccyx.

The method and apparatus for forming an anterior TASII axial boreinitially involves accessing an anterior sacral position, e.g. ananterior target point at about the junction of S1 and S2 depicted inFIGS. 1C and 1D. One (or more) visualized, imaginary, axialinstrumentation/implant line extends cephalad and axially in the axialaspect through the series of adjacent vertebral bodies to be fused orotherwise treated, L4 and L5 in this illustrated example. The visualizedAAIIL through L4, D4, L5 and D5 extends relatively straight from theanterior target point along S1 depicted in FIGS. 1C and 1D, but may becurved as to follow the curvature of the spinal column in the cephaladdirection.

It will be noted that the terms trans-sacral axial spinalinstrumentation/implant (TASII), and anterior axialinstrumentation/implant line (AAIIL), as used herein, are analogous tothe terms trans-sacral axial spinal instrumentation/fusion (TASIF), andanterior axial instrumentation/fusion line (AAIFL), The analogous termsgenerally refer to the same percutaneous pathways, the primarydifference being the types of treatments and implants delivered throughthe respective percutaneous pathways.

U.S. Pat. No. 6,575,979, issued Jun. 10, 2003, titled METHOD ANDAPPARATUS FOR PROVIDING POSTERIOR OR ANTERIOR TRANS-SACRAL ACCESS TOSPINAL VERTEBRAE, hereby incorporated in its entirety into thisdisclosure by reference, discloses in detail tools and methodology foraccessing targeted treatment sites, such as, for example,inter-vertebral motion segments.

Certain of the access and preparation surgical tools, as explained inU.S. Pat. No. 6,575,979, take the form of elongated solid body membersextending from proximal to distal ends thereof. Elongated solid bodymembers in medical terminology include, for example, relatively stiff orflexible needles of small diameter typically used to penetrate tissue,wire stylets typically used within electrical medical leads or cathetersto straighten, stiffen, or impart a curved shape to the catheter,guidewires that are used to traverse body vessel lumens and accessremote points therein (certain hollow body guidewires have lumens for anumber of uses), and obturators. Obturators are typically formed as rodsprovided in various diameters with blunt distal tips that can bemanipulated to penetrate, separate or manipulate surrounding tissuewithout cutting or damaging the tissue.

As used herein, the term “guide pin” can include solid body members(e.g., guidewires) employed to perform the functions of guide pindelivery and guidance described herein, unless the exclusive use of agiven one of such solid body members is explicitly stated. Such solidbody members can be stiff or flexible and can include distal anchoringmechanisms, e.g., sharpened or beveled tips.

Certain others of the surgical tools take the form of hollow body,tubular members having lumens extending from proximal to distal endsthereof. Such hollow body, tubular members can take the form of medicalcatheters, medical cannulas, medical tubes, hollow needles, trocars,sheaths, or the like, or variations thereof. Such hollow body tubularmembers employed in various embodiments described herein can be stiff orflexible and can include distal fixation mechanisms.

As used herein, anterior refers to in front of the spinal column(ventral) and posterior refers to behind the column (dorsal). As usedherein, proximal (caudal) refers the end or region that is closer to thesurgeon or sacral region of the spine, while distal (cephalad) refers tothe end or region that is closer to the patient's head.

In accordance with one aspect of the embodiments described herein, thereis provided a guide pin introducer that can be used to facilitate accessto the sacrum for delivery of at least one guide pin, which in turnserves as means over which other instruments of the surgical tools setcan subsequently be delivered to target sites to perform their intendedprocedural functions, individually or in combination, over or throughone another.

With reference to FIGS. 2A-B, in one aspect the guide pin introducer 100comprises an introducer tube 102 and an introducer handle 110. Theintroducer tube 102 extends between a distal end 104 and a proximal end106, and defines an inner, tubular member lumen 108. The length of thetube 102 is typically in the range of about 4″ (100 mm) to about 12″(310 mm), often about 5″ (120 mm) to about 9″ (230 mm). In one exemplaryembodiment, the length of the tube 102 is approximately 7″. The tube 102is preferably long enough to extend from a skin incision 190 near theparacoccygeal region, through the pre-sacral space, to an anteriortarget point 192, as shown, for example, in FIGS. 4 and 5.

With reference to FIGS. 3A and 3B, an exemplary embodiment of a guidepin introducer with multi-start thread 199 assembly engagement means isshown. The inner diameter (I.D.) of the introducer tube 102 is typicallyin the range of about 2 mm to about 5 mm, often about 3 mm to about 4mm. In one exemplary embodiment, I.D. of the tube 102 is about 3.5 mm(0.13″). The outer diameter (O.D.) of the tube 102 is typically in therange of about 4 mm to about 7 mm, often about 5 mm to about 6 mm. Inone exemplary embodiment, O.D. of the tube 102 is about 5.5 mm, with anI.D. dimensioned to slidably receive the distally located blunt tip 122of the stylet 119, as shown in FIGS. 2C-2E.

It will be noted that the actual dimensions (e.g, length, innerdiameter, outer diameter, etc.) of the tube 102 or any of the tools andcomponents parts thereof described herein will depend in part on thenature of the treatment procedure and the physical characteristics ofthe patient, as well as the construction materials and intendedfunctionality, as will be apparent to those of skill in the art.

The edge 105 at the distal end 104 of the tube 102 can comprise anynumber of configurations. In one embodiment, the edge 105 is atapproximately a 90 degree angle relative to the longitudinal axis of thetube 102. In another embodiment, the edge 105 is beveled at an anglerelative to the longitudinal axis of the tube 102. In one exemplaryembodiment, the edge 105 is beveled at an angle of about 45 degrees. Thetube 102 can be made from any of a number of known suitable materials,such as, for example, stainless steel, Ni—Ti alloys, or structuralpolymeric materials, or composites thereof.

With continued reference to FIGS. 4 and 5, in one mode of use, the guidepin introducer tube 102 serves as an enlarged diameter anterior tractsheath through which a guide pin, described in further detail below, canbe introduced into the targeted site 192.

With reference to FIG. 2A-2B, the introducer handle 110 extends betweena distal end 111 and a proximal end 113, and defines a tubular memberlumen 109 that is stepped or tapered toward the distal end 111. Thehandle 110 comprises a slot at its distal end which is dimensioned toreceive a section of the tube 102 beginning at the tube proximal end106. The handle 110 and tube 102 can be molded, machined or otherwiseformed as an integral unit, or can be affixed to each other by any of avariety of known attachment means, such as, for example, thermalbonding, adhesives, or press fits.

The introducer handle 110 can be made from any of a number of knownsuitable materials, such as, for example, polysulfone, polyvinylidenefluoride, polyethylenes, PEEK, or composites thereof. In one embodiment,introducer handle 110 is fabricated from an injection-molded part, madefrom an acetal-based copolymer, such as Delrin™ obtained from the DuPontCompany in Wilmington, Del., that is then machined with an I.D. of about13 mm (0.50″) and an O.D. of about 19 mm (0.75″). Here, the overalllength of the guide pin introducer 100 (i.e., the length of the tube 102and integral handle 110, in total) is about 300 mm (11.95″).

In accordance with one aspect of the embodiments described herein, thereis provided a stylet with a blunt distal tip that can inserted into theguide pin introducer described above to facilitate advancement of theguide pin introducer to the targeted site without causing damage tosurrounding tissue.

With reference to FIGS. 2D-E, in one embodiment, the stylet 119comprises an elongate body or rod 120 that extends between a distal end122 and a proximal end 124. The distal end 122 of the stylet rod 120preferably comprises a blunt tip, thereby preventing damage tosurrounding soft tissue as the guide pin introducer-stylet-pin-slotconfiguration assembly 134 (the approach assembly), which comprises theintroducer 100 and stylet 119, described in further detail below, isadvanced toward the targeted site, such as, for example, target point192, shown in FIG. 4B.

With reference to FIGS. 2C-2E and FIGS. 4 and 5, in order to advance theintroducer tube 102 through an anterior tract to the target point 192without concomitant damage to surrounding soft tissue, a stylet 119 canbe used in combination with the guide pin introducer 100 by advancingthe introducer-stylet-approach assembly 134 to the target area or point192.

The length of the rod 120 should be designed so that the stylet's blunttip 122 extends beyond the distal end 104 of the guide pin introducertube 102. In one embodiment, the rod 120 has an O.D. of about 3.2 mm(0.125″), which is less than the I.D. of the guide pin introducer 100.The stylet rod 120 can be made from any number of known suitablematerials, such as, for example, stainless steel or the like.

The stylet handle 126 extends between a distal end 128 and a proximalend 130, and comprises a distally located bore 129 to receive thesection of the stylet rod 120 beginning at the rod proximal end 124.

The length of the stylet handle 126 is typically in the range of about3″ (75 mm) to about 7″ (175 mm), often about 4″ (100 mm) to about 6″(150 mm). The O.D. of the handle 126 is typically in the range of about0.25″ (6 mm) to about 0.0.75″ (20 mm), and generally dimensioned tocooperate with the introducer handle 110 to form the introducer(approach) assembly 134.

In one embodiment, the stylet handle 126 has a diameter of about 12 mmto about 13 mm (e.g., about 0.50″) at the distal end 128 that increasesto about 20 mm (0.75″) at the proximal end 130. The length of theexposed rod 120 and narrow portion of the handle 126 together is about300 mm (12″) so that just the tip 122 of the stylet 119 will protrudefrom the distal end 104 of the introducer tube 102 upon assembly withthe guide pin introducer 100. The narrow portion of the stylet handle126 is configured to fit in a tubular member lumen 109 machined toreceive it within the handle 110 of the guide pin introducer 100.

The stylet handle 126 can be formed from any of a variety of materials,such as, for example, polymeric materials having desired properties(e.g., able to be machined or an injection-moldable polymer). Suitablematerials include, but are not limited to polysulfone, polyvinilydenefluoride, acetal-copolymer; acrylic, high density polyethylene, lowdensity polyethylene, nylon, polycarbonate, polypropylene, PVC, or thelike, or combinations thereof.

With reference to FIGS. 2A-2E and FIGS. 4 and 5, in one aspect, theguide pin introducer 100 can be provided with a releasable interlockthat prevents the blunt-tipped stylet 119 from retracting proximallywithin the lumens 108, 109 of the cannulated guide pin introducer 100,thereby maintaining the extension and exposure of the blunt tip 122 ofthe stylet 119 beyond the distal end 104 of the tube 102 as theintroducer (approach) assembly 134 is advanced by the surgeon toward thetarget point 192, optionally with the assistance of any known suitablevisualization technique.

The releasable lock may comprise any of a variety of interference fit orfriction fit surfaces carried by the stylet 119 for cooperating with acomplementary structure on the introducer 100. It will be noted that thereleasable interlock can be on and between any of the approach assembly134 components described herein.

In one embodiment, illustrated in FIGS. 2A-E the releasable interlock ofthe introducer 100 comprises a track 112 that is configured to acceptthe locking pin 139 of the stylet 119, described in further detailbelow. The handle 110 of the introducer 100 comprises an axiallyextending slot or track 112, machined or otherwise formed through thewall of the handle 110. Track 112 is positioned with an open endbeginning at the proximal end 113 and extends longitudinally in thedistal direction along the handle 110 with a circumferentially extendingnotch 107 at the distal end of the track 112.

The stylet handle 126 comprises a radially outwardly extendingengagement structure such as a locking pin 139 that is configured toslideably fit within the track 112 of the introducer handle 110. As thestylet handle 126 is advanced distally into engagement with theintroducer handle 110, the locking pin 139 advanced distally through theopening on the proximal end 113 of the introducer handle 110, and alongthe axially extending track 112. Once the stylet handle 126 has beenadvanced fully into engagement with the introducer handle 110, rotationof the stylet handle 126 with respect to the introducer handle 110advances the locking pin 139 into the circumferentially extending notch107. The locking pin 139 serves as an interior stop or locking lug thatreleasably secures the stylet handle 126 within the introducer handle110. In one embodiment, the locking pin 139 comprises a 0.125″ (3.2mm)×0.625″ (15.8 mm) dowel pin.

In one embodiment, shown in FIGS. 2D-2E, the approach assembly 134comprises the introducer 100 and the stylet 119 which are releasablyinterlocked to each other. The stylet handle 126 and the guide pinintroducer 100 can be mutually releasably engaged by the above-describedlocking pin 139, other complementary surface structures, twist-lockmechanisms, such as in a preferred multi-start thread configurationshown in FIGS. 3A-3E; a modified Luer lock, or any other known suitablemechanism that enables mechanical quick release (e.g., relative toanother embodiment that uses a press-fit method of engagement of therespective handles). With respect to the multi-start threadconfiguration shown in FIGS. 3A-3E, the guide pin introducer 100 hasinternal threads 199 on the proximal end 113 that engage with externalthreads 198 on stylet handle 126. Engagement and disengagement of theassembly 134′ is by means of twist-lock. These quick release mechanismsfacilitate disengagement of the stylet handle 126 from the guide pinintroducer handle 110 once the distal end 104 of the guide pinintroducer tube 102 is brought into relatively close proximity to thetarget 192. The stylet 119 can be disengaged from the rest of theapproach assembly 134 and removed from the patient's body.

With reference to FIGS. 2D-2E, in one exemplary method of use, thestylet 119 is inserted into the lumens 108, 109 of the introducer tube100 in a manner and configuration such that the blunt tip 122 extendsand is preferably exposed from about 1 mm to about 2 mm beyond thedistal end 104 of the guide pin introducer 100. In this manner, theblunt tip 122 of the stylet 119 serves as a soft tissue dilator thatassists in the safe and atraumatic positioning of the distal end 104 ofthe guide pin introducer tube 102 in close proximity to the anteriortarget site 192.

The stylet rod 120 is inserted into the cylindrical polymeric handle 126so that about 200 mm (about 7.76″) of the rod 120 extends out of thehandle 126, into and through introducer tube 102, and beyond theintroducer tube distal end 104, so that the distal end blunt tip 122 ofthe rod 120 is exposed at the distal most end of the approach orintroducer assembly 134.

As shown in FIGS. 4 and 5, in one exemplary method of use, the spine isaccessed via a small skin puncture 190 adjacent to the tip of the coccyxbone. The pre-sacral space is entered using any known suitablepercutaneous technique. The introducer assembly 134, with the stylet'sblunt tip 122 serving as a dilator, is advanced through theparacoccygeal entry site. Once the tip 122 of the stylet 119 is advancedthrough the facial layer, the blunt tip 122 is positioned against theanterior face of the sacrum and advanced along the anterior surface ofthe sacrum to the desired position or targeted site 192—here, the S1vertebral body. In one embodiment, the distal portion of the approachassembly 134 is advanced to the targeted site under fluoroscopicguidance, as is described in co-pending U.S. patent application Ser. No.10/125,771, filed on Apr. 18, 2002, titled METHOD AND APPARATUS FORSPINAL AUGMENTATION.

The stylet 119 is released and removed from the approach assembly 134after the distal portion of the assembly 134 is advanced to the targetedsite 192, thereby leaving the distal portion of the introducer 100 atthe targeted site, to preface the introduction of a guide pin throughtthe introducter 100 to the targeted site 192.

In accordance with one aspect of the embodiments described herein, thereis provided a guide pin that can be delivered to the targeted sitethrough the use of a guide pin introducer, such as, for example,introducer 100 described above. In one embodiment, shown in FIG. 7A theguide pin assembly 140 has an elongate guide pin 142 that extendsbetween a distal end 144 and a proximal end 146. The guide pin assembly140 also has a sharp guide pin tip 145 at the distal end 144 and apreferably releasable handle 150 engaged at the proximal end 146.

The length of the guide pin 142 is typically in the range of about 9″ toabout 15″, often about 11″ to about 13″. In one exemplary embodiment,the length of the guide pin 142 is approximately 12″. The length of theguide pin 142 is typically sufficiently long so that the tip 145 extendsbeyond the distal end 104 of the guide pin introducer tube 102 when theguide pin assembly 140 is inserted within the introducer 100, as shownin FIG. 7E.

The guide pin 142 can be made from any of a number of suitablematerials, such as, for example, stainless steel, NiTi alloys, orcomposites thereof. In one embodiment, the guide pin 142 is formed fromsubstantially the same materials (e.g., stainless steel) as the stylet119 and comprises a solid, elongated body 142 with an O.D. of betweenabout 2.2 mm (0.090″) to about 3.4 mm (0.13″) and a length of aboutbetween about 300 mm (12.00″)-600 mm (24″).

Unlike the stylet 119, the guide pin tip 145 is not blunt, and may beshaped according to one among various configurations. In one embodiment,not illustrated, the guide pin tip is formed as a simple conical or twosided wedge pointed tip. In another embodiment, shown in FIG. 6B, thetip 145′ is formed as a trocar tip that has a three-sided bevel at 15degrees. In still another embodiment, shown in FIG. 6C, the tip 145″ isformed as a beveled tip that has one side beveled at an angle. The anglecan range, for example, from about 30 degrees to about 60 degreesrelative to the longitudinal axis of the guide pin 142. The selection ofthe tip 145 geometry is influenced by the need to initially tack theguide pin 142 into the target, such as, for example, the sacral face,without having the guide pin 142 slip off or slide up the targetsurface. Pointed tip geometries enable the guide pin 142 to snag thesacral face, and thus eliminate “skidding” effects that may otherwiseaccompany tapping the target surface.

With continued reference to FIG. 7A-7D, in one embodiment, the guide pinassembly 140 comprises a guide pin handle 150′ that comprises a distalend 152′ and a proximal end 154′, and comprises a distally located lumen175 to receive a section of the guide pin 142′ beginning at the guidepin proximal end 146′. In one aspect, the guide pin handle assembly 180shown in FIG. 7F comprising the guide pin handle 150 and thumb/set screwelement 170 is configured to align and releasably engage the guide pin142. In method of use, for example, a flat on guide pin 142 (see FIG.6D) is positioned in a predetermined relationship to the bevel on guidepin tip 145, so that when the guide pin is assembled and locked withinthe guide pin handle, wherein the thumb screw is advanced against theflat of the guide pin, this enables the clinician to determine, withreference to the thumb screw, visual or tactile indicia on the proximalhandle which will indicate the rotational orientation of the beveledtip. Thus in this manner, the surgeon is able to determine, and adjustor “steer” the guide pin tip 145 position. In another aspect ofalignment and releasable engagement mechanisms, the guide pin handleassembly 180 comprises a metal hexagonal or square socket 178 within theinsert 172 of the guide pin handle assembly 180 when mated with theproximal end of the guide pin hex 181 and flat 182 (FIG. 6D) it providesa positive stop precluding longitudinal and rotational motion of theguide pin 142 relative to the guide pin handle 150.

In one embodiment, the handle 150 has an O.D. of about 12 mm (0.50″) onits distal end 152, an O.D. of about 20 mm (0.75″) on its proximal end154, and is approximately 100 mm (4″) in length. A bore 175 is formed inthe distal end 152 extending substantially through the guide pin handel150, of about 3.5 mm (0.13″) (i.e., substantially the same as the O.D.of the guide pin 142), into which the guide pin 142 can be releasablyinserted.

The guide pin handle 150 can be formed from any of a variety ofmaterials, such as, for example, polymeric materials having desiredproperties (e.g., able to be machined or an injection-moldable polymer).Suitable materials include but are not limited to sterilizable polymericmaterials, e.g., polyvinilidine fluoride; polysulfone; acetal-copolymer;acrylic, high density polyethylene, low density polyethylene, nylon,polycarbonate, polypropylene, PVC, or the like, or combinations thereof.

The guide pin handle 150 is configured to be able to “steer” a guide pin142 in the event that there is axial misalignment of the its afterinsertion. In the context of the present invention, “steer” refers to anability to manipulate by turning and make controlled positionaladjustments of a guide pin 142 once it is tapped through the corticalbone of its anterior target 192. Specifically, the thumb/set screw 170(FIG. 7C) serves as a point of reference to the tip 145 orientation andis particularly configured to mark the alignment of the guide pin'sbeveled tip 145, as opposed to the face of the beveled plane. When theguide pin is advanced it will tend to deviate in the direction ofbeveled tip, which is indicated, e.g., by the thumb screw. For example,if upon insertion the beveled plane of the tip 145 faces anterior, theguide pin 142 will track in the posterior direction when advanced.

While the visualization of the guide pin 142 in situ is facilitated, forexample, by fluoroscopy, resolution limitations are frequently lessideal with respect to the guide pin tip 145 configuration. For thisreason, the addition of the set screw 155 and thus the ability to steerthe guide pin 142 via its handle 150 represent a significant proceduraladvantage enabled by the tools and techniques of the present invention.

One exemplary method of use involves: advancing the distal portion of adelivery assembly 159 to the targeted site; removing the guide pinhandle 150; removing the introducer 100; and leaving the guide pin 142at, and attached to, the targeted site 192. In one approach, the guidepin handle 150 and the introducer 100 are removed separately. In anotherapproach, the handle 150 and the introducer 100 are removed together,leaving only the guide pin 142 in place.

Disengagement of the guide pin handle 150 from the proximal end 146 ofthe guide pin 142 enables extension of the guide pin's elongate bodylength through the addition of an extension 160 that can be attached toextend the length of the pins, thereby resulting in an extended guidepin, such as, for example, the long guide pin 164″ of FIG. 8A whichextends between a distal end 144″ and a proximal end 146″.

In accordance with one aspect of the embodiments described herein, thereis provided a guide pin that can be extended in length to facilitate thesubsequent delivery and utilization of other access and preparationtools.

With reference to FIG. 8G, in one embodiment, the guide pin 142 can beextended in length along its longitudinal axis via the addition of anextension 160, which has a connector 162 on its distal end. In thisexemplary embodiment, the extension 160 comprises an exchange pin, andthe connector 162 comprises a roll pin.

The guide pin 142 has a bore that is located at its proximal end 146 andthat is dimensioned to receive a distal portion of the connector 162.The extension 160 has a bore that is located at its distal end and thatis dimensioned to receive a proximal portion of the connector 162.

In one embodiment, the guide pin 142, extension 160, and connector 162are releasably interconnected by any known suitable approach, such as,for example, an interference fit or friction fit or the like. In oneembodiment, the connector 162 is fixedly secured to the distal end ofthe extension 160 and the connector is releasably secured to theproximal end of the guide pin 142.

With reference to FIGS. 8A-F, in a preferred embodiment, the extendedguide pin 164″ comprises a guide pin 142″ and an extension 160″ that areconnected to each other through the use of a connector 165, whichprotrudes from the distal end of the extension 160″. The proximal end ofthe guide pin 142″ has a threaded bore 148 at its proximal end 146″ thatis dimensioned to receive the connector 165.

In this preferred embodiment, the connector 165 comprises a threadedstud. The connector 165 extends between a distal end 166 and a proximalend 167 and has a smaller outer diameter towards its distal end 166, ascompared to the larger outer diameter toward its proximal end 167. Theconnector 165 comprises screw threads 168 for releasably securing theextension 160″ to the guide pin 142″, which itself has a threaded bore148 having threads 149 that is complementary to the threads 168 of theconnector 165.

The length of the extended guide pins (e.g., 164, 164″) can range fromabout 400 mm to about 800 mm, often about 500 mm to about 700 mm. In oneembodiment, the length of pin 164 is about 600 mm (24.00″).

In one exemplary method of use, following the delivery of theintroducer-stylet approach assembly 134 to the targeted site 192 andremoval of the stylet 119 from the introducer 100, a guide pin-guide pinhandle assembly 140 is inserted into the cannulated guide pin introducer100. As the guide pin 142 is initially tapped into the sacrum it is ineffect serving as a bone dilator. Once the guide pin tip 145 has beeninserted (tapped) into the anterior face of the S1 vertebral body, theguide pin introducer 100 and the guide pin handle 150 are removed, toenable engagement of the guide pin 142 with the guide pin extension 160.

Subsequent components from among the surgical tools sets describedherein, which generally have a greater O.D. than the extended guide pin164, are introduced to the target site 192 by concentric passage overthe extended guide pin 164. The subsequent components can be advancedover the extended pin 164 individually or in combination, over orthrough one another, to the targeted site 192. For example, in oneapproach, the first tools in the sequence of instruments to be deliveredover the guide pin 164 are bone dilators, described in further detailbelow.

In accordance with one aspect of the embodiments described herein, thereare provided certain materials which can enhance visualization of toolsvia radio-imaging (e.g., fluoroscopy). Examples of such materialsinclude stainless steel where tools or portions thereof comprise metal,and powders, such as barium sulfate, for components configured frompolymeric materials, e.g., bushings, that may be inserted within thebody cavity. It will be understood that such materials can beincorporated during the formation of certain metal or polymericcompounds comprised in the surgical tools sets and devices disclosedherein.

Although dilation of soft tissue is common for certain surgeries,dilation of bone tissue is generally not a common technique fororthopedic procedures. In one approach, dilating bone in the spineinvolves: widening the axial pathway or channel in preparation forsubsequent treatments by compressing cancellous bone or cortical boneshell to the side rather than removal via cutting or coring such bonematerial.

Compression is usually a less traumatic procedure than coring with, forexample, an electrically powered drill, as the latter may inadvertentlycut or tear soft tissue, including nerves or blood vessels. Lessbleeding of the bone occurs with dilation, which is an unanticipatedbenefit. It is believed that the compression of the bone by the dilatorresults in a tamponade effect so that the amount of bleeding from boneaccompanying this procedure is reduced. Compression appears to affordstronger “anchoring”, for subsequent implants (e.g., implants withthreading) within an inter-vertebral space. It is also possible thatcompression may have a long term beneficial impact via the initiation ofsubsequent osteogenic (bone growth) effects.

In accordance with one aspect of the embodiments described herein, thereare provided bone dilators that can be used to create and widen one ormore channels in the vertebral bodies for the ensuing passage of otherinstruments and devices. In one embodiment, the dilators are cannulatedand can be delivered accurately to the target site, following removal ofany preceding dilators, in succession one after another, each directlyover the guide pin. In another embodiment, the dilators are configuredto pass concentrically over a previously delivered smaller dilator(i.e., a dilator having a relatively smaller O.D than the ID ofsuccessive dilators.), without the extraction of the smaller dilatorover the guide pin.

With reference to FIGS. 11-12, in one embodiment, the dilator 200comprises a cannulated dilator rod 202 extending between a distal end204 and a proximal end 206, and defines an inner lumen 212. The dilator200 comprises a tapered dilator tip 208 with a distal end opening 214 atthe distal end 204 and a handle 210 at the proximal end 206.

The length of the cannulated dilator 202 is typically in the range ofabout 150 mm to about 450 mm, often about 250 mm to about 350 mm. In oneexemplary embodiment, the length of the rod 202 is approximately 300 mm(12.00″).

The I.D. of the cannulated dilator rod 202 is typically in the range ofabout 2.5 mm to about 4.5 mm, often about 3 mm to about 4 mm. In oneembodiment, the rod 202 has an I.D. slightly larger than about 3.5 mm(i.e., greater that the O.D. of the extended guide pin 164) and an O.D.of about 6 mm. FIG. 10 illustrates three bone dilators 2001, 2002, and2003 having O.D. of 6 mm, 8 mm, and 10 mm, respectively.

The tapered dilator tip 208 is usually tapered at about 5 to about 45degrees from O.D. to I.D. In one embodiment, the tip 208 of the dilator200 is tapered at approximately 8 degrees from O.D. to I.D. In anotherembodiment, the tip 208 is tapered at about 13 degrees from O.D. to I.D.

The cannulated dilator rods 202 can be made from any known suitablematerial, such as, for example, stainless steel, aluminum, or compositesthereof. In one embodiment, the dilator 200 and its component parts aremachined from stainless steel tubing. Here, each dilator 200 has ahandle 210 that is affixed to the dilator proximal end 206. The handle210 is about 100 mm (4.00″) long and is engaged (e.g., by welding; pressfit, etc) in the middle to assure a secure fit with the rod. Withreference to FIGS. 13A-C, in one embodiment, there is provided a largedilator construct 199, configured as a dilator sheath 220 and a dilatorrod assembly 200 _(L) that comprises a dilator shaft 202 _(L) a dilatorhandle 210 _(L) and two pins 218 as engagement means for the construct199 The cannulated dilator shaft 202 _(L) extends between a distal end204 _(L) and a proximal end 206 _(L) and defines an inner lumen 212_(L). The shaft 202 _(L) comprises a tapered tip 208 _(L) with a distalend opening 214 _(L) at the distal end 204 _(L). The dilator rodassembly 200 _(L) comprises pins 218 extending out from the outer wallof the dilator shaft 202 _(L).

The length of the cannulated dilator rod assembly 200 _(L) is typicallyin the range of about 8″ to about 16″, often about 11″ to about 13″. Inone embodiment, length of the dilator rod assembly 200 _(L) isapproximately 300 mm (12.00″). In one embodiment, the larger diameterproximal end 206 _(L) of the dilator shaft 202 _(L) is about 75 mm (3″)in length while the overall length of the dilator rod assembly 200 _(L)is about 300 mm. (12.00″).

In one embodiment, the cannulated dilator shaft 202 _(L) has twodifferent outer diameters. More specifically, there is a smallerdiameter section of the dilator shaft 202 _(L) configured to be coveredby the sheath 220. The O.Ds. are typically in the range of about 5 mm toabout 12 mm, often about 6 mm to about 11 mm. In a preferred embodiment,the dilator shaft 202 _(L) has a smaller O.D. of about 9 mm (0.35″) anda larger O.D. of about 10 mm. The I.D. of the dilator shaft 202 _(L) istypically in the range of about 2.5 mm to about 4.5 mm, often about 3 mmto about 4 mm.

The tapered dilator tip 208 _(L) is usually tapered at about 5 to about45 degrees from O.D. to I.D. In one embodiment, the tip 208 _(L) of thedilator shaft 202 _(L) is tapered at about 13 degrees from O.D. to I.D.In one preferred embodiment, this taper of tip 208 _(L) is substantiallythe same as the taper of the tip 226 at the distal end 222 of thedilator sheath 220.

The sheath 220 comprises a sheath tube 221 that extends between a distalend 222 and a proximal end 224, and is configured to be releasablyattachable to the dilator rod assembly 200 _(L). In one embodiment, thesheath tube 221 comprises a tip 226 at the distal end 222 and two tracks(one shown) 229 machined into the wall of the tube 221, that ispositioned to begin at the proximal end 224 and extend longitudinallyalong the sheath tube 221 with a slight circumferential notch at thedistal end of the track 229.

The track 229 accepts the pin 218 mounted on the dilator shaft 202 _(L),thereby providing a releasable interlock of the dilator shaft 202 _(L)with the sheath 220. In another embodiment, the large dilator construct199 comprises any known suitable releasable lock comprising any of avariety of interference fit or friction fit surfaces carried by thedilator shaft 202 _(L) for cooperating with a complementary structure onthe sheath 220.

In one embodiment, the large dilator construct 199 comprises two tracks229 and two locking lugs 218. In another embodiment, the large dilatorconstruct 199 comprises one track 229 and one pin 218.

Both the dilator shaft 202 _(L), the sheath 220, and their respectivecomponent parts can be made from any known suitable material, such as,for example, stainless steel, aluminum, or composites thereof. Thesheath 220 is preferably fabricated from a material of sufficientstiffiness to maintain its structural integrity when other access andpreparation tools are subsequently introduced and utilized through thesheath cannula.

In one embodiment, the distal end 222 of the sheath 220 is beveled tomatch the taper of the dilator tip 208 _(L) of the large dilator rodassembly 200 _(L) (e.g., 10 mm dilator), thereby facilitating insertionof the rod 202 _(L) into the sheath 220.

The length of the sheath 220 is typically in the range of about 7″ toabout 10″, often about 8″ to about 9″. In one embodiment, the sheath 220is approximately 200 mm (8.5″) in length.

The wall thickness of the sheath 220 is typically in the range of about0.005″ to about 0.040″, often about 0.008″ to about 0.030″. In oneembodiment, the sheath 220 has an I.D. of about 9 mm (0.35″) and an O.D.of about 10.5 mm (0.413″).

The actual dimensions of the large dilator rod assembly 200 _(L) and itscomponents will depend in part on the nature of the treatment procedureand the anatomical characteristics of the patient. For example, the O.D.is about 9.5 mm (0.375″) for a sheath 220 used in treating relativelysmaller patients, while the O.D. for the same is about 10.5 mm. (0.413″)for relatively larger patients. As shown in FIG. 13C, in one embodiment,there is provided a distal end taper 228 as a transition to enable useof a smaller distal OD dilator sheath 220 (e.g., 0.375″) with a sturdierproximal wall thickness, where clinically appropriate. In anotherembodiment, there is no taper to the distal end of the dilator sheath220′ (FIG. 13D). In another embodiment, the sheath 220, 220′ has abeveled tip 226 at the distal end 222, which facilitates docking of thesheath 220, 220′ to the targeted site 192, i.e., the anterior surface ofthe S1 vertebral body.

The large dilator rod assembly 200 _(L) is preferably releasablyinterlocked to the proximal end 224 of the dilator sheath 220 and ispreferably capable of being released and removed thereby facilitatingthe withdrawal of the large dilator rod assembly 200 _(L) while leavingthe sheath 220 to serve as a working cannula into the targeted site,such as, for example, the anterior surface of the S1 vertebral body.

With reference to FIG. 9, in one exemplary method of use, the dilator200 is tapped with a cannulated slap hammer 230 that slides onto theextended guide pin 164. Successive movements distally and proximallyover the extended guide pin 164 that repeatedly tap against the dilatorhandle 210 will to advance the dilator, longitudinally, into the sacrum.In one embodiment (not shown), the hammer 230 has a flat on it to giveanother hammering surface, as well as for ease of use, where theadditional flat prevents the hammer from rolling off of the table.

The use of the slap hammer 230 engaged on the extended guide pin 164, asopposed for example, to the use of an unengaged mallet in “free space”on the proximal end 206 of a dilator 200, enables the surgeon to focushis attention on the visualization monitor while simultaneously tappingand dilating. The axial alignment of the slap hammer 230 resulting fromits use in combination with the extended guide pin 164 is advantageousin that it transfers force solely in the longitudinal direction, whichprecludes misshapen pathways or misalignment of subsequently introducedtools.

In one embodiment, the hammer 230 has a length of about 4″ (100 mm). TheI.D. of the cannulated hammer 230 is configured to slide over the guidepin. In one exemplary embodiment, the hammer has a lumen ID of about 3.5mm (0.13″). The cannulated slap hammer 230 can be made from any knownsuitable material, such as, for example, stainless steel or the like.

With reference to FIG. 10, in one exemplary method of use, a series ofbone dilators 200 ₁, 200 ₂, and 200 ₃, having O.D. of 6 mm, 8 mm, and 10mm, respectively, are advanced directly over the guide wire 164, andtapped with a slap hammer 230 to progressively widen the intervertebralchannel in a stepwise manner. The last and largest dilator 200 _(L) (200₃ in the present embodiment) is assembled with a sheath 220. The dilator200 _(L) can be inserted as a preface to the subsequent introduction ofsuccessive instruments in the surgical tools sets described herein. Thelarge dilator sheath 220 is preferably left behind to serve as aprotected portal to the target location.

In one embodiment, the dilators and sheaths (e.g., sheath 220) arecoated with a surfactant, hydrophilic hydrogel, or the like tofacilitate passage of surgical tools and/or implants through the sheath220. In another embodiment, the surgical tools and/or implants insertedinto the sheath 220 are coated with a surfactant, hydrophilic hydrogel,or the like.

In accordance with one aspect of the embodiments described herein, thereare provided twist drills that can be used to extend the working channelwithin the spine, such as, for example, a channel that extends cephaladfrom the anterior surface of the S1 vertebral body.

With reference to FIG. 14, there is provided a twist drill with handle300 that a configured as a twist drill 301 having a distal end 302comprising a fluted section 306 with helical flutes 308 and a proximalend 304, and a handle 310 engaged at the proximal end 304 of the twistdrill 301. The helical flutes 308 facilitate boring as the handle 310 isturned in the appropriate direction—here, clockwise to advance the twistdrill 301 distally into the working channel.

The twist drill with handle 300 is typically fabricated from hardenedstainless steel or the like. The length of the twist drill with handle300 typically ranges from about 11″ (275 mm) to about 13″ 330 mm. In oneembodiment, the twist drill with handle 300 is approximately 300 mm(12.00″) long. The twist drill with handle 300 typically ranges indiameter from about 5 mm (0.20″) to about 13 mm (0.50″). In oneembodiment, the twist drill with handle 300 has a diameter of about 9mm.

In one mode of use, the twist drill with handle 300 is used to extendthe working channel in the spine to the treatment area (e.g., a discspace) after bone dilators are used to expand the diameter of theproximal portion or entry/targeted site 192 of the working channel.

In one exemplary method of use, where the targeted site 192 is theanterior surface of a sacral vertebral body and where the dermal entrysite is near the paracoccygeal region, a twist drill with handle 300having an O.D. of about 9 mm and is inserted into the lumen at theproximal end 224 of the dilator sheaths 220 or 220′, each of which isused as a protected portal to the sacrum. The twist drill with handle300 is advanced by turning the handle 310 at the proximal end 304 of thetwist drill 301 so that the helical flutes 308 at the distal end 302 ofthe twist drill 301 progressively bore into and penetrate through thesuperior S1 bone end plate and into the L5-S1 disc space. Followingnucleectomy and preparation of the disc space by means of the cuttersand tissue extraction tools and methods described below, the twist drillwith handle 300 can again be used to penetrate the L5 inferior bone endplate and vertebral body, prior to the removal of the dilator sheath 220or 220′, using, for example, a 6 mm or a 7.5 mm twist drill with handle300 as needed based on the patient's anatomy.

In one mode of use, the twist drill with handle 300 is used to drillabout halfway into the depth of the L5 vertebral body in preparation forsubsequent anchoring of implants, or through the vertebral body to gainaxial access to more distal inter-vertebral disc spaces, e.g., L4-L5,for therapeutic procedures.

In one embodiment, not illustrated, the twist drill unit comprises abushing portion configured to compensate for the (mismatch) differencesbetween the I.D. of the dilator sheath 220 or 220′ and the O.D. of thetwist drill with handle 300, thereby precluding “wobble” in the discspace en route to the L5 target, and thus enabling on-center axialalignment and use. The bushing portion is preferably located on thetwist drill 301 near the proximal end 304 that is sufficiently distantfrom the distal end 302 so that it remains within the confines of thedilator sheath 220 or 220′ during operation of the tool for its intendedpurpose. In one embodiment, the bushing portion is made from a polymer,such as, for example, Delrin™, PTFE, PVDF, or the like. In a preferredembodiment the bushing is integral with the twist drill 301, i.e.,formed from the same rod blank.

On advantage of the present embodiment is that the twist drillconfiguration, mode of delivery, and use at the target site are nolonger dependent on electrical or motorized drilling, therebyeliminating the risks of tissue damage associated with electric drillslippage and recoil.

In accordance with one aspect of the embodiments described herein, thereare provided nucleectomy and cutting tools and techniques havingadvantages over conventional cutting tools and techniques. Certainconventional procedures rely on brute force to scrape, tear or breakaway the material. For example, rongeurs, or “pliers-like” devices, areoften utilized to reach in through an access hole cut into the annulus,grab an amount of nucleus tissue and then to rip it out. In anotherexample, curettes or various flat blades with sharpened edges areinserted and scrapped against the bone in an attempt to separate thenucleus from the bone. Another conventional approach involves usingenzymes, such as, for example, chemopapain, to chemically dissolve orbreak-down the nuclear tissue. Such conventional approaches andtechniques are often inexact, incomplete and potentially dangerous tothe patient. Often the extent of the surgical exposure, and thereforethe resulting trauma, is dictated by the nucleus removal procedure andnot the subsequent fusion or repair procedure, which is the true endgoal of the procedure. In contrast to the conventional techniques,methods, and instrumentation described above, the apparatuses andmethods described herein are not reliant on the application of strengthand high forces and are designed be more effective in complete removalof tissue and clean preparation of any bone surfaces.

Co-pending U.S. patent application Ser. No. 10/853,476, filed May 25,2004, teaches various types of instrumentation and techniques for theremoval of tissues and preparation of treatment sites in the spine, suchas, for example, inter-vertebral motion segments located within thelumbar and sacral regions.

With respect to the present invention, it is anticipated that one ormore nucleectomies can be performed extending into successively cephaladintervertebral disc spaces. For example, a disc recess 354′ is depictedin disc L4-L5 A wide variety of cutter blade and edge configurations asbore enlarging means can be employed to perform nucleectomies of theL5-S1 354, and L4-L5 354′ disc spaces, wherein the cutter means aredelivered and operated through the anterior TASII axial bore(s). Certainof these methods are described in further detail in U.S. patentapplication Ser. No. 09/710,369, the content of which is incorporated inits entirety into this disclosure by reference.

Co-pending U.S. patent application Ser. No. 09/782,534, filed on Feb.13, 2001, teaches various types of techniques for using cutting toolsfor removing disc material and preparation of spinal treatment sitesthat comprise a spinal disc, for example, a method of removing at leasta portion of the nucleus through a TASII axial bore while leaving theannulus AF intact.

Referring to FIG. 15, a nucleectomy instrument 400 is inserted throughthe axially aligned anterior tract 372 defined by the lumen of thedilator sheath 220 and the TASII axial bore 370. The nucleectomyinstrument 400 comprises a cutting blade (e.g., cutter blade 453 whichrefers collectively to any blade configuration) which is remotelymanipulatable, i.e., a retracted cutter blade 453 is first advancedthrough the TASII axial bore 370 and then extended laterally into thenucleus of the spinal disc. More specifically, the cutting blade 453 ismounted into an extendible or steerable distal end section 382 ofnucleectomy instrument, i.e. cutter assembly 400 extending through theTASII axial bore 370 and anterior tract 372.

The cutter assembly 400, cutter blade 454 and cutter assembly shaft 410are shown schematically in FIGS. 16-18 and not necessarily to scale toone another or to the TASII axial bore 370.

In accordance with one aspect of the embodiments described herein, thereare provided surgical cutters that can be used to perform nucleectomyvia insertion into a disc space to excise, fragment and otherwise loosennucleus pulposus and cartilage from endplates from within the disccavity and from inferior and superior bone end plate surfaces. Thecutters described herein represent a significant advance to currentclinical techniques for access and preparation of intervertebral bodiesfor the subsequent insertion of therapeutic devices, such as prostheticnucleus and fusion implants, and in particular for axially alignedimplants, or for insertion of therapeutic materials, e.g., forosteogenesis, spinal arthroplasty, or annuloplasty.

With reference to the exemplary embodiments of FIGS. 16A-C, the cutterassembly 400 comprises: a cutter shaft 410 extending between a distalend 412 and a proximal end 414; a cutter blade 453 at the distal end412; a handle 416 at the proximal end 414; a cutter sheath 430 placedconcentrically over the shaft 410; and a shaft sleeve 418 at the distalend 412.

It will be understood, however, that the cutter components andstructures described herein are suitable for the assembly andapplication of cutter assemblies that comprise, for example, up-cutters452, debulkers 450, down-cutters 454, or the like, or variationsthereof. In FIGS. 16A-16E, the cutter comprises a down-cutter 454. Inanother embodiment, the cutter comprises an up-cutter 452 (see FIG. 16H)In still another embodiment, the cutter comprises a debulker 450 (seeFIGS. 17A-E). These and other types of cutters are described in furtherdetail below, with reference to preferred embodiments which compriseteardrop-shaped cutter blades 460, 460′, 490, 490′, 490″ shown in FIGS.18A-18G.

With reference to the embodiments of FIGS. 16C and 17A, in assemblingthe cutter assembly 400, the longitudinal portion 406 of the cutterblade (e.g., debulker 450, up-cutter 452, or down-cutter 454) is placedinto a slot 413 near the distal end 412 of the shaft 410. In oneembodiment, the cutter blade hole 407 is aligned with a strategicallyplaced cutter shaft hole 411 within the shaft slot 413.

The shaft slot 413 is dimensioned to accommodate a cutter blade 453 suchas, for example, a debulker 450 (17A), an up-cutter 452, a down-cutter454 (16C), or the like, or variations thereof. The width of the slot 413is approximately the same as the width of the longitudinal portion 406of the cutter blade 453. The curvature at the distal end of the slot 413accommodates the curvature of the cutter blade 453 between thelongitudinal portion 406 and the laterally extending portion of theblade arm 402 (which defines the reach or throw of the cutter blade453). The slot 413 provides torsional support to the cutter blade arm402 while the curvature at the distal end of the slot 413 provides axialsupport to the cutter blade arm 402, necessary, in conjunction withcutter blade edge geometries (described in detail below; see FIGS.16D-6H and 17B-17E, and 18A-18F) to the cutting effectiveness of thecutter blade 453.

A shaft sleeve 418 may be placed over the assembly shown in FIGS. 16Cand 17A comprising the shaft 410 and the cutter blade 453. The shaftsleeve 418 when pinned effectively serves to align and fix the shaft 410and the longitudinal portion 406 of the cutter blade 453. While any ofvariety of other fastening techniques may also be used, the preferredpin technique is described below.

In one embodiment, the shaft sleeve 418 comprises a strategically placedshaft sleeve hole 419 that aligns with the cutter shaft hole 411 of theshaft slot 413 and the cutter blade hole 407. The sleeve 418 can besecuredly fixed to the rest of the assembly by inserting a cross pin 409through the shaft sleeve 418 and the longitudinal portion 406 of thecutter blade 453 into the shaft 410. In one embodiment, the cross pin409 that fixes the cutter blade 453 to the shaft 410 is approximately0.06″ in diameter. The rest of the assembly 400 components can befixedly secured to each other using any known suitable fixationmechanisms, as described in further detail below.

With reference to an exemplary embodiment in FIGS. 16D-E, the cutterblade 453 (as shown, a down-cutter 454) comprises a blade arm 402 and alongitudinally-extending portion 406. The blade arm 402 begins from theproximally-located, longitudinally-extending portion 406, and extendslaterally to comprise any number of suitable shapes or configurations,such as, for example, a “J” shape or “S” shape, as shown. It isunderstood that in the context of the present invention, configurationsof the types as just described may comprise a plurality of cutter bladearms 402. In a preferred embodiment, described in further detail below,the cutter blade 453 comprises a “teardrop” shape (460, 460′, 490, 490′,490″) shown in FIGS. 18A-18G.

The cutter blades 453 generally comprise at least one sharpened cutterblade edge 401 (collective). With reference to FIGS. 16D-E, in oneembodiment, the cutter blade arms 402 (collective) of the down-cutters454 have three cutter blade edges 401 including cutter blade arms 402′(proximal), and 402″ (distal) separated lateral bend 403. In otherwords, the cutter blade edges may be continuous with each other aroundthe lateral bend 403 or may be interrupted. The illustrated blade edges401 are illustrated on a leading surface 405 of the cutter blade arm402. A trailing surface 415 is illustrated as a blunt side, without asharpened cutter blade edge 401. Since the cutter blade edges 401 are onthe same (leading) edge or side of the cutter blade arms 402, the cutterblade 454 is considered to be single-sided in this regard. In thisembodiment, the single-sided cutter blade arms 402 cut when turned in aclockwise manner but do not cut when rotated in a counter-clockwisedirection. The direction of the rotation (clockwise or counterclockwise)is determined from a perspective that is proximal relative to thedistally-located cutter. In another embodiment, not illustrated, thecutter blade arms 402 have cutter blade edges 401 on both the leadingsurface 405 and trailing surface 415 of the cutter blade arms 402, sothat cutting can be accomplished with this double-sided cutter bladearms 402 by means of either clockwise or counterclockwise rotation.

As will be described in further detail below, all of the cutter bladeedges 401 disclosed herein may be optimally configured for preparing anintervertebral motion segment for either a subsequent fusion procedureor a subsequent procedure in which mobility of the intervertebral motionis to be preserved. More specifically, for nucleectomies precedingfusion procedures, cutter blade edges 401—regardless of cutter blade arm402 configuration—will contact the spinal disc inferior or superiorendplates, while for mobility procedures, the cutter blade edges 401will be spaced apart from the spinal disc endplates.

As an example, referring to FIG. 16G, there is illustrated across-sectional view through cutter blade arm 402 of the cutter blade454 illustrated in FIG. 16E. In that illustrated embodiment, a leadingside 405 is provided with a sharpened edge 420 fabricated by means ofcutting, grinding or other manufacturing technique. The sharpened edge420 is formed at the intersection of the declined face 421 and thesurface 424 of the cutter blade arm 402′ and 402″. This cutter blade 454configuration is optimized for use against an inferior endplate inpreparation for a fusion procedure. When the proximal surface 424 isplaced in contact with an inferior endplate of a spinal disc and rotatedin a clockwise direction, the sharpened edge 420 on leading surface 405will scrape against said endplate. This can be used to scrape away thecartilaginous endplate and roughen the vascularized vertebral body so asto cause bleeding, which is desirable in order to facilitate bone growthand achieve fusion of the vertebral bodies that are superior andinferior to the spinal disc being treated.

However, in a procedure to prepare the nucleus space for implantation ofa mobility preserving device, roughening the endplate of the spinal discmay be undesirable. As shown in FIG. 16F, for this procedure, thesharpened edge 420′ is desirably positioned at the intersection of theinclined face 421 and the surface 424, such as by mirroring the angle ofinclination of the declined face 421. In this configuration, thesharpened edge 420′ will be spaced apart from the inferior endplate ofthe spinal disc by a distance which is equal to the thickness of theproximal cutter blade arm 402′, thereby minimizing the chance of thebone bleeding, that would promote unwanted fusion.

With respect to the cutter arm blade 402, the mirrored blade of proximalcutter blade arm 402′ is shown in FIG. 16F and FIG. 16G as distal cutterblade arm 402″.

A sharpened edge (not shown) may alternatively be positioned partwaybetween the proximal surface 422 and the distal surface 424, such asproviding a first and second inclined face on the leading surface 405,which intersect at a sharpened edge 420. In the atraumatic cutterdesign, intended for use in preparation for a procedure which preservesmobility, the sharpened edge 420 is preferably spaced apart from thesurface of the cutter adapted for sliding contact with a boney endplate. Although the sharpened edge 420 may optimally be spaced apartfrom the bone contacting surface by the full thickness of the cutterblade, as discussed above, a sharpened edge 420 may be positionedin-between the proximal surface 422 and the distal surface 424 by asufficient distance to prevent injury to the bone. The distal andproximal orientation of the sharpened edge 420 described above may bemirrored on a given cutter blade, depending upon whether the cutter isintended to be placed in sliding contact with an inferior or superiorspinal disc endplate, as will be apparent to those of skill in the artin view of the disclosure herein. Again, the foregoing sharpened edgeorientation may be applied to any of the cutter configurations disclosedherein.

In one embodiment, shown in FIG. 16H, the cutter of the assembly 400comprises an up-cutter blade 452. As with the above-describeddown-cutter blade 454, the up-cutter blade 452 generally comprises acutter blade arm 402 and a longitudinally extending base portion 406.The cutter blade arm 402 begins from a proximally located,longitudinally extending base portion 406 that extends generallydistally and inclines laterally outwardly to a radial limit 404. The arm402 curves to form a proximally facing concavity with a distal limit.The cutter may comprise any number of suitable shapes or configurations,such as, for example, a “J” or question mark shape. In anotherembodiment, described below, the cutter comprises a “teardrop” shape.

With reference to the embodiments shown in FIGS. 16D-H, the down-cutters454 and up-cutters 452 have single-sided blade arms 402 that are bent atan angle from between about 40 degrees to about 140 degrees relative tothe longitudinally extending portion 406. The blade arms 402 canoptionally be canted between about 5 to about 25 degrees, preferablyabout 15 degrees, so that the cutting edge is rotated radially outwardlyrelative to the trailing edge. The blades arms 402 of the up-cutters 452and down-cutters 454 are preferably angled vertically steeper relativeto the longitudinal axes of the shafts to which they are affixed, ascompared to those of debulkers 450, described in further detail below.

The tilt of the blade arm 402 in the proximal direction in FIGS. 16D,16E and 16H is configured to allow for maximum engagement of the bladecutting edge with the distally facing surface of the bone end plate,while severing nucleus material. Thus, for an up-cutter 452, an angleless than about 90 degrees relative to the axis of the shaft 410generally would not enable adequate engagement of the blade cuttingedge(s) 401 with the superior bone end plate. For a down-cutter 454, anangle greater than about 90 degrees relative to the axis of the shaft410 generally would not facilitate adequate engagement of the bladecutting edge with the inferior bone end plate, and a blade arm 402 atabout a 40 degree angle of tilt of the blade arm 402 operates preferably(is “vertically steeper”) than one at 70 degrees.

The “throw” i.e., the reach of the blade arm 402 is measured from thecentral longitudinal axis of the cutter shaft 410 radially outward toits radial limit 404 (FIG. 16H). In other words, blade arm throw as usedherein refers to the radius of the circle cut by a full revolution ofthe blade arm.

For up-cutters 452 and down-cutters 454, the blade arm 402 throw aregenerally within the range of from about 6 mm to about 18 mm. In oneembodiment, the blade arm throw of the cutters 452, 454 are about 12 mm.

In accordance with one aspect of the embodiments described herein, thecutter blade of the assembly 400 comprises a debulker 450 Up-cutters 452and down-cutters 454, as illustrated in FIGS. 16D, 16E and 16H may notbe ideal initiators of nucleus tissue fragmentation. For one, theirblade arms 402 and cutting edges 401 do not easily bend or sweep withoutspace, particularly in terms of angles, having first been created by oneor more debulkers 450.

With reference to FIGS. 17B-E, a debulker 450 comprises a cutter bladearm 402 that begins from a proximally-located, longitudinally-extendingbase portion 406 and extends laterally to comprise any number ofsuitable shapes or configurations, such as, for example, a “J” or “U”shape, as shown.

In one embodiment, the debulker 450 comprises a shorter throw than thecutter blade 454, which allows debulkers 450 to retain their shapebetter than cutters with longer arms upon initial entry into the discspace, providing improved engagement of effective cutting edge surfacewith nucleus material. FIGS. 17B-C illustrated one embodiment of arelatively smaller sized debulker 450. FIGS. 17D-E show one embodimentof a debulker 450′ having a greater cutting radius.

In one embodiment, the blade arm 402 configuration of a debulker 450resembles a “J” in shape. The functional advantage of such bladevertical elements in the “J” shape is the increased efficiency ofcutting per unit of throw or the increased cutting edge surface contactwith the material to be fragmented.

In the embodiments of FIGS. 17B-C and 17D-E, the debulkers 450, 450′have single-sided blades (i.e., cutter blade edges 401 on one of thecutter lateral sides). In another embodiment, not illustrated, thedebulkers 450 have double-sided blades (i.e., blade edges on both of thecutter lateral edges), which enables bi-directional cutting when thecutter handle 416 is manipulated to rotate the blade arm 402.

In one mode of operation, debulkers 500 with shorter arm lengths, andhence shorter “throws” in terms of circumferential cutting diameter, arefirst introduced through the large dilator sheath 220 into the discspace and used to fragment the tissue within the disc space. In one modeof operation, one or more down-cutters, up-cutters, or the like, orvariations thereof are used to further fragment the tissue within thedisc space.

In accordance with one aspect of the embodiments described herein, thereare provided cutters that comprise a closed loop such as a “teardrop”shape configuration, which provides more cutter rigidity and reduces therisk of fracture of the cutters during use (e.g., when a leading cuttingedge of the cutter becomes embedded in bone during use). It will beunderstood that the any of the cutters (e.g., down-cutters, up-cutters,debulkers) described herein can comprise a “teardrop” or other closedloop shape.

Cutters (e.g., debulkers, up-cutters, down-cutters, etc.) that comprisea closed loop generally provide a more robust and overall more efficientcutting device that can be used for any number of surgical procedures,such as, for example, nucleectomy. Closed loop cutters may have avariety of advantages over cutters having only a single attachment pointto the rotatable support. For example, in one embodiment, the closedloop shape allows for two fully supported cutting edges (e.g., top andbottom) on any given lateral side of the cutter. The closed loop shapealso allows for side or end edges in the curve where the blade or cutterarm doubles back on itself.

With reference to embodiment shown in FIGS. 18A-B, there is provided astandard size closed loop debulker 460. In the illustrated embodiment,the cutter arm 462 of the closed loop debulker 460 doubles back uponitself to form a distal segment 470 and a proximal segment 468. Both thedistal segment 470 and proximal segment 468 are secured to the rotatableshaft 410, resulting in the distribution of any stress in the arm 462over two segments rather than over a single segment arm. The distributedstress can result from the torque of turning the shaft 410 or theresistance of the disc material on the blade(s) 461.

The arm 462 of the closed loop cutter begins from a proximally locatedend 480, extends distally to provide an attachment surface and thenlaterally outward to form the lower segment 468. The arm 462 thendoubles back at juncture 482, the location of which defines the cuttingradius. The arm 462 then extends laterally inward, turns, and thenproximally toward proximal end 484, to provide an attachment surface.The proximal and distal segments 468, 470 each comprise a sharp edge461.

The distal segment 470 comprises an attachment structure such as a slot472 near the proximally located end 484. The lower segment 468 alsocomprises an attachment structure such as a cutter blade hole 467 nearthe proximally located end 480. The shaft slot 472 enables end 470 toslide relative to the cross pin 409 during extension and retraction ofthe cutter blade (e.g., 460 or 490) of the assembly 400.

With reference to the embodiment shown in FIGS. 18C-D, there is provideda large teardrop shaped debulker 460′, having a longer laterallyextending portion and longer blades 461′, relative to the debulker 460of FIGS. 18A-B. A longer teardrop configuration generally allows forfurther reach than smaller ones. In general, the cutter blades 460,460′, 490, 490′ of FIG. 18A-FIG. 18D, when rotated through a completerevolution will cut a transversely circular cavity having a diameterwithin the range of from about 10 mm to about 30 mm.

In each of the closed loop cutters illustrated in FIGS. 18A through 18D,the proximal segment 468, 468′ and distal segment 470, 470′ extendradially outwardly from the axis of rotation generally in parallel witheach other. However, alternative configurations may also be used, suchas by imparting curvature to one or both of the proximal segment 468 anddistal segment 470. One or both of the segments may be provided with acurve having a concavity facing in the distal direction; a concavityfacing in the proximal direction, or concavities opposite to each other,depending upon the desired clinical result. In addition, in theillustrated embodiments, the cutter blade arm 462 formed by the proximalsegment 468 and distal segment 470 extends radially outwardly atapproximately a 90 degree angle from the longitudinal axis of therotatable shaft 410. The cutter blade arm 462 may alternatively beinclined in either a proximal or distal direction (not shown) dependingupon the desired performance, and, for example, whether the cutter isintended to operate against an inferior or superior spinal discendplate. For example, the cutter blade arm 462 may incline in a distaldirection or a proximal direction by as much as 45 degrees away from theperpendicular.

With reference to the embodiments shown in FIGS. 18E, 18F, and 18G,there are provided teardrop shaped down-cutters 490, 490′, 490″ havinglarge, medium, and small sizes, respectively. The length of the teardropshaped cutters varies in the range between about 0.25″ to about 1.00″.These arcuate cutters can extend linearly within a deployment sheath and“curve” as they are advanced distally out of the sheath into the discspace, instead of extending axially until fully deployed from the sheathand then “flopping over” which requires a lateral advance through thenucleus material as well as sufficient axial clearance to allowdeployment within the disc. Due to the limited disc height in mostfusion/mobility patients, the cutter preferably has a low profile duringextension, use, and retraction. Straight bladed cutters will extendlinearly in the axial direction of the deployment sheath duringextension and long versions may actually hit the upper endplate, causingthe cutter to get stuck or inhibiting complete deployment.

With reference to the exemplary embodiment of FIG. 18E, the double-backstructure of the teardrop down-cutter 490 begins from a proximallylocated end 480, extends distally along the lower segment 468, extendslaterally outward and downward (i.e., proximally) to form a proximallyfacing concavity, along the lower segment 468, doubles back at juncture482, extends laterally inward and upward (i.e., distally), and thenextends proximally along the upper segment 470 toward proximally locatedend 484. At least one and preferably both of lower and upper segments468, 470 comprise a blade 461.

The upper segment 470 comprises a slot 472 near the proximally locatedend 484. The lower segment 468 comprises a cutter blade hole (not shown)near the proximally located 480. The shaft slot 472 enables end 484 toslide relative to the cross pin 409 during extension and retraction ofthe cutter blade (e.g., 490, 490′, 490″) of the assembly 400.

In the embodiments illustrated in FIGS. 18E through 18G, the separationdistance between the first and second cutting edges is a controllablevariable in manufactureine (e.g., predetermined during cutter bladeformation, i.e., heat treatment of the pinned Nitinol shape memoryalloy) and varies from about 2 mm to about 8 mm, and, often is about 3mm to about 4 mm. The maximum separation 483 in the illustratedembodiment is located within about the radially outwardly most one thirdof the total blade length. Alternatively, the maximum separation 483 maybe positioned within the radially inwardly most third of the bladelength, or within a central region of the blade length, depending uponthe desired deployment and cutting characteristics.

In accordance with one aspect of the embodiments described herein, theblade arms 402 and the cutter blades 453 in general can be formed fromstrip material that is preferably a shape memory alloy in its austeniticphase at room and body temperature and that ranges in width from about0.10-0.20″ and in thickness from about 0.015-0.050″. Blade arms 402formed in accordance with the present embodiment are generally able tobe flexed in excess of 100 cycles without significant shape loss, andtwisted more than 1 and ±2 full turns (about 540 degrees) withoutbreakage.

In one embodiment, the cutting blade 453 and cutter blade edge 401 isformed from a super-elastic, shape memory metal alloy that preferablyexhibits biocompatibility and substantial shape recovery when strainedto 12%. One known suitable material that approximates the preferredbiomechanical specifications for cutter blades 453 and cutter bladeedges 401 and blade arms 402 is an alloy of nickel and titanium (e.g.,Ni₅₆ Ti₄₅ and other alloying elements, by weight), such as, for example,Nitinol strip material #SE508, available from Nitinol Devices andComponents, Inc. in Fremont, Calif. This material exhibits substantiallyfull shape recovery (i.e., recovered elongation when strained from about6%-10%, which is a factor of ten better than the recovered elongation atthese strain levels of stainless steel).

The shape and length of the formed cutter blade 453 in general variesfor the different cutting modes. The shape memory material can be formedinto the desired cutter blade 453 configuration by means of pinningalloy material to a special forming fixture, followed by a heat-set,time-temperature process, as follows: placing the Nitinol strip (withthe blade's cutting edge(s) 401 already ground) into the forming fixtureand secured with bolts; and placing the entire fixture into the oven ata temperature ranging from about 500° C. to about 550° C. (e.g., whereoptimum temperature for one fixture is about 525° C.) for a time rangingfrom between about 15 to about 40 minutes (e.g., where the optimum timefor one fixture is about 20 minutes). Flexible cutter blades formed fromNitinol in this manner are particularly suited for retraction into ashaft sleeve, and are able to be extended to a right angle into the discspace. Moreover, they are able to mechanically withstand a large numberof cutting “cycles” before failure would occur.

The cutting blade edges 401 are preferably ground with accuracy andreproducibly. The angle of the inclined surface (e.g., 421, 421′, 461,461′. 461″) of the blade relative to the blades's flat side surfacetypically ranges from about 5 degrees to about 60 degrees, often about20 degrees to about 40 degrees. In one embodiment, the blade angle isapproximately 30 degrees relative to the blade's side surface.

In one embodiment, the shaft 410 of the assembly 400 is formed fromsolid stainless steel or other known suitable material. In oneembodiment, the shaft has a diameter of approximately 0.25″ (6.3 mm).The shaft sleeve 418 may be formed from stainless steel tubing or otherknown suitable material tubing, and has a length of about 0.7″.

The cutter sheath 430 can be fabricated from polymeric material,stainless steel, or other metal tubing. The sheath 430 typically has anouter diameter (O.D.) of about 0.31″ (7 mm) to about 0.35″ (9 mm). Withreference to FIG. 161, in a preferred embodiment, the sheath 430 isconfigured with a shoulder 499 bored into its inner wall which serves asa stop that precludes the shaft 410, along with its attached blade arm402 and handle 416, from becoming fully disengaged from the cuttersheath 430 when the blade arm 402 is retracted into the sheath 430. Whenretracted proximally, the proximal end of the shaft sleeve 418 bumpsinto the shoulder 499, thereby preventing the shaft 410 from being fullydisengaged from the sheath 430. It will be understood that one or moreanalogous shoulder structures can be implemented in any of the toolsdescribed herein, such as, for example, the sheaths used with the tissueextractors, etc.

In accordance with one aspect of the embodiments described herein, thereis provided a handle configured as a lever which is affixed to theproximal end of the cutter shaft. Referring to FIGS. 16A-B, theillustrated handle 416 is affixed to the proximal end 414 of the cuttershaft by means of a cross-pin set screw 415, which reduces the risk ofhandle 416 disengagement from the cutter shaft 410 (e.g., unthreading byrotational manipulation during cutting). The handle 416 is preferablyaffixed so that it is in rotational positional alignment with the bladearm 402 and serves as a reference marker for the blade arm's in situorientation.

In one embodiment, the handle 416 of the cutter assembly 400 isconfigured as a turn knob fabricated from a polymeric material, such as,for example, ABS polymer or the like, that is injection moldable andthat may be machined, and is affixed to the cutter shaft 410 by means ofthreaded or other engagement to the cutter shaft proximal end 414.

The handle 416 may serve as a stop against which the proximal end of thecutter sheath 430 abuts, thereby maintaining the engagement of the shaft410 and cutter sheath 430, when the blade arm 402 is extended distallyand is exposed from the distal end of the cutter tube lumen, forexample, as a result of having pushed on the handle 416 to advance theshaft 410 distally to expose the cutter blade 453 and cutter blade edge401.

Due to the inevitable accumulation of severed tissue on and within thedebulker 250 and other cutter assembly components (e.g., up-cutters 452,down-cutters 454, etc.), it is preferred that they be disposable. Inaccordance with one aspect of the embodiments described herein, thereare provided cutter assembly components that are disposable. Two orthree or four our more of any of these components may be provided in akit, enabling the clinician to dispose of one as desired and tointroduce a new one into the procedure.

In accordance with one aspect of the embodiments described herein, thereare provided blade arms and cutters that are designed to be rotated andused in one direction (i.e., clockwise or counter-clockwise). In oneaspect, for the single-sided cutter blades 450 illustrated in FIGS.17B-C, rotational motion of blade arms 402 in only one direction (e.g.,clockwise) will initiate severing of nucleus material (see alsoup-cutters 452 and down-cutters 454 described herein). The intendedmotion during the use of these blades 401 is similar to the back andforth motion of a windshield wiper—wherein the excision with respect tothese cutters occurs in the sweep that is clockwise in direction.

In one embodiment (not shown), one or more stops are placed within thecutter shaft 410 to control blade arc or range of motion. In anotherembodiment (not shown), one or more stops are fitted onto the dilatorsheath 220 to control the blade arc or range of motion.

The shaft 410, cutter sheath 430 and the handle 416 components arepreferably co-configured to enable the cutter blade arm 402 and theshaft 410 to which it is attached be able to be “pushed-pulled” so as toretract the blade arm 402 into and extended the blade arm 402 from thelumen 434 at the distal end 432 of the cutter guide tube 430, as needed.More specifically, the cutter blade edges(s) 401 of the cutter blade 453are retracted into the cutter sheath 430 for delivery into the discspace. Once the sheath 430 is in position, the cutter blade edges (s)401 are extended distally and rotated using the handle 416 to cutnucleus material. The cutter blade edge(s) 401 are again retracted intothe cutter sheath 430 for removal of the cutter assembly unit 400 fromthe spine.

In one mode of use, particularly suitable for performing a nucleectomyof the L5-S1 intervertebral disc space, a series of cutting toolscomprising debulkers, up-cutters, and/or down-cutters are used toseparate disc material (e.g., nucleus pulposus and cartilage from withinthe disc space).

In one embodiment, the terms “debulking”, “up-cutting”, and“down-cutting” refer to the blade arms configurations that are used in asequential and progressive fragmentation of the core nucleus pulposuswithin the central or core portion of the disc, the surface of thesuperior bone end plate, and the surface of the inferior bone end plate,respectively.

In one method of use, one or more debulkers 450, with blade arm lengthssuccessively increasing from about 8 mm to about 15 mm, are used in theinitial steps of performing nucleectomy. In one mode of operation, threedebulkers—namely, a small debulker 450 _(S), a medium debulker 450 _(M),and a large debulker 450 _(L)—having blade arm lengths of about 8 mm, 11mm, and 15 mm, respectively, are used prior to introduction of thecutters (e.g., up-cutters 452 and/or down-cutters 454).

In accordance with one aspect of the embodiments described herein, thereare provided cutter configurations that advantageously enable thesurgeon to have more precision and control with respect to the excisionof nucleus material from the endplates. Some level of bone bleeding isgenerally associated with decortication (i.e., the scraping of thecutters against the surfaces of the end plates). Such bleeding canadvantageously promote bone healing and/or osteogenesis in the normallya vascular area of the disc. This is particularly advantageous when thedisc space is being prepared for subsequent procedures or implants wherethere is a need for accompanying bone growth. The cutter configurationsand techniques of the present invention assist the surgeon in achievingan appropriate amount of bleeding in a controlled manner which does nototherwise compromise the bone endplate or adjacent structures.

In accordance with one aspect of the embodiments described herein, thereare provided extraction tools for extracting tissue fragments from atreatment site, such as, for example, a disc space. While the extractiontools and devices are described in the context of their application tothe removal of nucleus pulposus and cartilage material excised from thea spinal disc via axial access to a disc space, it will be understoodthat they can be used to remove other tissue fragments from the same ordifferent treatment sites, or for lateral access into a disc space aswell.

The extractor devices include configurations that can be inserted intothe disc space through an axial approach to the lumbar spine. Suchconfigurations include, but are not limited to, “wheel”, “end” or“bottle” multifilament configurations. At the same time, the toolsshould be small enough to allow atraumatic entry into the disc via acannulae (e.g., the large dilator sheath). The extractor tools aregenerally used to remove tissue fragments in the treatment site bysnagging and pulling them out.

With reference to the embodiment of FIGS. 19A-D, there is provided aretractable tissue extractor 500 comprising an elongate extractor shaft512 that extends between a distal end 514 and a proximal end 516. Theextractor 500 preferaby comprises a delivery sheath 520 that extendsbetween a distal end 522 and a proximal end 524.

The extractor 500 comprises an extractor head 509 engaged with thedistal end 514 and a handle 518 affixed to the proximal end 516. Theextractor head 509 may be glued and pinned into or otherwise attached tothe distally located receiving section of the extraction tool 500. Theextractor handle 518 may be configured, constructed, and affixed to theextractor shaft in accordance with substantially the same means andmaterials as previously described and disclosed herein for cutterhandles.

The extractor assembly 500 of FIGS. 19A-D is shown in its “pre-splayed”state, which refers to a first configuration or first, reduced crosssectional profile in which the filaments or wires 530 of the extractorhead 509 on the distal end of extractor assembly 500 are in a reducedcross sectional orientation, to facilitate assembly into the shaft 512.In one aspect, the “pre-splayed” individual wires or filaments 530 ofextractor head 509 are comprised as part of a multi-filar and/ormulti-layer wound coil. The windings of the layers can be left-handedand/or right-handed., although it is preferred that all layers be woundin the same direction., and that a wound configuration for theindividual filaments is preferable to a straight-filament configurationin order to assure that the filaments 530 will retain a helical orcoiled configuration when unwound.

In the context of the present invention, as used herein the termsspiral, helical, or kinked refer to the fact that the filaments are notstraight, and it is understood that they are not necessarily “uniformly”formed (e.g., not as reproducibly spaced coils).

In one embodiment, the extractor head 509 may be formed from a cablethat is wound as 4 concentrically coiled, multi-filar layers (e.g., 6,7, 8, 9 filaments or filars per layer) fabricated from thehighest-tensile strength stainless steel wires commercially available.As will be described below, it is the combination of the tensilestrength, diameter and helical or coiled configuration of the wires 530when unraveled enable wire entanglement to effectively extract tissuefragments. The extractor head 509 is capable of being transformed from afirst “pre-splayed” state (e.g., where the wires are wound together in acable that has a bundle diameter of about 0.15″) to a second, “splayed”state (i.e., a second, expanded cross sectional profile) by theunwinding of the wires 530 (e.g., stainless steel wires) with diametersof about 0.01″.

With reference to FIG. 20, there is provided one embodiment of theextractor assembly 500 (with the extractor head 509 in a splayed state)that can be used to remove entrapped tissue fragments 502 from thetreatment site. As shown, the tissue fragments 502 are entangled in theinter-wire spaces of the multiple strands 530.

In one embodiment, the extractor head 509, once unraveled and splayed,the reach or total spread of the extraction filaments 530, tip-to-tip isfrom about 0.50″ to about 1.50″. In a preferred embodiment, the reach ofthe extraction filaments 530 tip-to-tip is about 1.00″.

The wires or filaments 530 are preferably stainless steel and of adiameter and tensile strengths, that enable retraction and deliverythrough the delivery sheath 520 without deforming extensively e.g., theindividual filaments 530 retain their helical configuration andcollectively maintain the radial reach of extractor head 509. Inalternative embodiments, the wires can comprise, nickle alloys,nickel-titanium alloys, cobalt alloys, or the like.

In one embodiment, shown in FIGS. 21C-D, the helical wires 530 of theextractor head 509 are splayed in a non-uniform pattern, so that thewires 530 overlap with each other. The wires 530 are preferablysufficiently stiff to snag tissue fragments 502, yet be pliable enoughto compress and bend when tugged with tissue fragments 502 in tow. Themechanical properties, number, and spatial relationship among of thewires 530 impact effective tissue extraction of tissue fragments 502 aswill be explained below.

Tissue fragments 502 are captured by the extractor head 509 in part as aresult of the wires' surface areas, in part due to their own(inter-wire) physical entanglement with a concomitant entrapment ofadditional material as the extractor tool 500 is manually rotated ortwisted and the spatial orientation among wires 530 changes. The tips atthe distal end of the wires 530 are also sharp to assist in snagging.

The wires 530, however, are preferably not so stiff as to precludedeflection upon contact with stiffer/more solid elements other thanfragmented and loosened tissue. The tissue extractor wires 530 arepreferably soft enough to deform and conform to the irregularities ofthe bone surface and neither cut or erode other vertebral structures,such as bone or the annulus, so there is also no concomitant risk offurther spine or spinal cord damage.

The density of wires 530 within the disc space is also a significantfactor with respect to maximum tissue removal. When wire or bristledensity (# wires per unit volume of disc space) is too high, theextractor head 509 tends to push material to the disc perimeter ratherthan collecting it. In one embodiment, the extractor head 509 comprisesabout 30 wires 530, each with a diameter of about 0.010″. The disc spaceis typically small, with a cavity volume of about 6-8 cc, so a densitywith too many wires 530 (e.g., 50 strands, each with a diameter of about0.010″), precludes their optimum interaction in removing tissue fragment502. Extractor heads having at least about 5 to about 10, but often nomore than about 40 or 50 strands, depending upon strand length anddiameter, and desired clinical performance, are contemplated.

In one embodiment, the proximal end 534 of the wire cable comprising theextractor head 509 is brazed to the extractor shaft 512, which is formedof stainless steel tubing. In another embodiment, (FIG. 19B), theproximal end 534 of the extractor head 509 is affixed to the extractorshaft 512 by means of a pin 508, as well as adhesively affixed. Any of avariety of other attachment techniques may also be used, such as gluing,crimping and various potting techniques. Alternatively, the extractorhead 509 may be sufficiently axially enlongated to extend to theproximal end 516 of the extractor shaft 512.

In one embodiment, the shaft 512 is formed from a solid polymer rod.Suitable rod materials include, but are not limited to, polymers whichare machined and/or injection molded, and are able to be sterilized.Examples of such materials include acetal copolymer, acrylic,polyethylene, nylon, polycarbonate, polypropylene, PVC, ABS, or thelike.

In one embodiment, the extractor shaft 512 is about 0.25″ in diameterand is approximately 12.00″ in length. As previously noted, theextractor assembly 500 should be small enough to allow atraumatic entryinto the disc via a cannulae (e.g., the large dilator sheath 220).

In one embodiment, the extractor sheath 520 is formed from stainlesssteel tubing with an I.D. of about 0.26″ and an O.D. of about 0.35″.

With reference to FIGS. 19A-19C, the extractor shaft 512 also maycomprise a handle 518 that is affixed to its proximal end 516, tofacilitate manipulation of the tool when removing tissue, and also toenable extension and retraction of the extractor head 509 as noted anddescribed elsewhere. In order to prevent over-extension andover-retraction the extractor assembly 500 comprises stop means. Onesuch stop means is shown in FIG. 19A, comprising a stop pin 515 and aslot 562. The stop pin 515 is affixed to the shaft 512 and configured toextend through slot 526 in the extractor sheath 520. The length of theslot 526 limits the travel of the pin and in turn the shaft 512,limiting extension and retraction of the shaft 512 and thus theextractor head 509. In one embodiment, the handle 518, which is oflarger diameter then the extractor sheath 520, serves as an extensionstop. More specifically, distance between the proximal end 524 of thesheath 520 and the distal end of the handle 518 controls the amount ofexposure of the extractor head 509. A longer distance between end 524and the handle 518 will result in an extractor 500 with a shaft 512 thatcan be distally advanced a longer distance, thereby resulting inincreased exposure of the extractor head 509.

With reference to FIG. 16I, as was previously described with respect tothe cutter sheath 430, in a preferred embodiment, the extractor sheath520 is configured with a shoulder 499 bored into its inner wall whichserves as a stop that precludes the shaft 512, along with its extractorhead 509 and handle 518, from becoming fully disengaged from theextractor sheath 520 when the extractor head 509 is retracted into theextractor sheath 520.

With reference to FIGS. 22A-B, in another aspect, the extractor head 509comprises wires(s) 550 at least some of which, and in one embodiment allof which, are configured with hooks 558 on the distal ends 554 of thestrands 550, for extracting tissue. The wires 550 are constructed from ametal such as stainless steel with a wire strand diameter from about0.004″ to about 0.020″. Again, for the extended extractor head 509, thereach or total spread of the hooked wires 550, tip-to-tip is from about0.50″ to about 1.50″. In a preferred embodiment, the reach of theextraction filaments 530 tip-to-tip is about 1.00″.

The extractor head 509 comprising the hooked wires 550 is affixed to theextractor shaft 512 in substantially the same manner as previouslydescribed, above. In this embodiment as just described it is the hookedconfiguration of the wires 550 which extract tissue fragments 502 asopposed to the entanglement among individual wires with respect to thepreferred kinked fimaments 530., The hooked wires 550 are configured soas not to excise, abrade, or otherwise compromise adjacent structures(e.g., the annulus).

Extractor heads 509 configured according to the embodiment of FIGS.22A-B can snag material for removal with a lower strand density (i.e.,number of strands per unit volume of disc space). In one approach, asfew as two strands can be used operatively. Again, if the density ofstrands 550 is too high, the extractor head 509 tends to push tissuefragments 502 to the disc perimeter rather than collect it. In oneembodiment, the head comprises fewer than about 30 wires 550.

With reference to FIGS. 19A-D and 21A-D, there is provided an extractorsheath 520 which restrains the extractor head 509 in the first, reducedconfiguration, which is retracted into or extended from the lumen at thedistal end 522 of the extractor sheath 520 as the extractor assemblyunit 500 is inserted or removed from the disc space, through theprotected portal of the large dilator sheath 220.

In one mode of use, the targeted tissue site comprises a disc space andthe tissue fragments to be extracted comprise nucleus material. In onemode of use, the extractor 500 is used to remove nucleus material aftertissue cutters (e.g., debulkers, down-cutters, up-cutters, etc.) havebeen used to loosen up nucleus material within the disc cavity and endplate surfaces. In another approach, extractors 500 are usedconcurrently with the tissue cutters. In one method of use,approximately five extractor assembly units 500 are utilized in eachprocedure (i.e., during the nucleectomy of one disc).

In one embodiment, the extractor assembly 500 is a disposable, one-timeuse unit. Here, each extractor head 510 is only inserted once, in situ,into a disc cavity.

In accordance with one aspect of the embodiments described herein, thereare provided various material inserters than can be used to deliver anynumber of suitable materials to a treatment site.

In accordance with one aspect of the embodiments described herein, thereis provided a bone graft insertion tool that can be used to insert andpack bone material or paste into the disc following nucleectomy.

With reference to FIGS. 23A-D, in one embodiment, the bone graftinserter assembly (or bone growth material inserter) 600 comprises apacking instrument 602 and a delivery cannula 604, as shown in FIGS. 23Cand 23D.

Referring to FIG. 23C, the packing instrument or packer 602 comprises arod 610 that extends between a distal end 612 and a proximal end 614. Inone embodiment, the rod is made from stainless steel or the like. Therod 610 is configured to be inserted into a central lumen extendingthrough the delivery cannula 604. In one embodiment, the rod 610 has adiameter of about 0.156″.

The packer 602 comprises an impactor mass such as a ball or handle 616which may be attached to the proximal end 614. In one embodiment, theimpactor ball 616 is press fit to the proximal end 614. The ball 616 ispreferably solid and may be formed from a polymeric material, such as,for example, an acetal copolymer. In one embodiment, the ball 616comprises a bore or aperture for receiving the proximal end 614 of therod 610. In one embodiment, this bore is about 0.15″ in diameter andabout 0.50″ deep. In one embodiment, the diameter of the ball is about1.00″.

The illustrated packer 602 comprises a bushing 618 attached to thedistal end 612. In one embodiment, the bushing 618 is press fit to thedistal end 612. The bushing 618 may be a solid cylindrical structure andformed from a known suitable polymeric material. In one embodiment, theO.D. of the bushing 618 is about 0.29″.

In one embodiment, the bushing 618 comprises one or more O-rings 619which provides a tight sliding fit between the bushing 618 and theinside wall of the central lumen extending through the delivery cannula604, enabling insertion of bone growth facilitation materials which areless viscous, e.g., paste or liquid.

Referring to FIG. 23D, the delivery cannula 604 comprises a tube 620that extends between a distal end 622 and a proximal end 624. In oneembodiment, the tube 620 is machined from stainless steel tubing with anO.D. of about 0.31″ and an I.D. of about 0.30″.

The distal end 622 of the cannula 604 comprises a tip 626 that ispreferably beveled at an angle to facilitate directional control ofmaterial as it is delivered into the treatment site, such as, forexample, a disc space. In one embodiment, the tip 626 is beveled at anangle of approximately 45 degrees relative to the longitudinal axis ofthe cannula 604.

The proximal end 624 of the cannula 604 comprises a funnel 628. In oneembodiment, the distal portion of the funnel 628 has an I.D. of about0.30″. The funnel increases in diameter toward its proximal end. In oneembodiment, the funnel 628 is engaged with the tube 620 via brazing. Inanother embodiment the funnel 628 is engaged with the tube 620 by meansof press fit. In one embodiment, the overall length of the tube 620 andfunnel 628 is about 13.00″. The funnel 628 may be fabricated from apolymeric material such as acetal copolymer.

In one mode of use, the cannula 604 is docked or otherwise secured tothe entry to the treatment site. Bone paste or osteogenic material isinserted into the cannula 604 via the cannula tip 626 or by means of thefunnel 628. The packer 602 is inserted into the funnel 628 and advanceddistally to push bone paste out of the cannula distal end 622 and intothe treatment site (e.g., a disc space). In one embodiment, as thepacking rod 610 is advanced distally into the cannula 604, the impactorball 616 hits the funnel 628 just as the bushing 618 reaches the distalend 622 of the cannula 604.

In accordance with another aspect of the embodiments described herein,FIGS. 24A-24B illustrate a bone paste inserter 640 comprising acannulated tube 642 that extends between a distal end 644 and a proximalend 646. The tube 642 defines an inner lumen 648.

A preferred assembly 640 also comprises a distally-located threadedportion 650 that may be formed directly on the tube 642 or engaged tothe distal end 644 via any known suitable attachment technique. Thethreaded portion 650 is configured to engage with the threaded proximalends of implants (e.g., and axial fusion rod) to facilitate the deliveryof bone paste into the treatment site. In another embodiment, theassembly 640 lacks a threaded portion 650.

The assembly 640 also comprises a quick connect fitting such as a luerlock 652 at the proximal end 646. In one embodiment, the luer lock 652is a 10 gauge luer lock. The tube 642 and threaded portion 650 istypically machined from stainless steel or other suitable material knownin the art.

In one mode of use, bone paste is delivered through the paste inserterassembly 640 beginning at the luer lock 652, and through the tube 642,and into the treatment site via distal end 644.

In accordance with one aspect of the embodiments described herein, thereis provided an allograft placement tool. With reference to FIGS. 25A-C,in one embodiment, the allograft placement tool (or augmentationmaterial inserter) 950 comprises a cannulated tube 952 that extendsbetween a distal end 954 and a proximal end 956, and that defines aninner lumen 955.

The tool 950 comprises an allograft delivery tip 958 attached to thedistal end 954 via any known suitable attachment technique, such as, forexample, press-fit, adhesive material, or the like. In one embodiment,the tip 958 is secured to the tube 952 with one or more pins 953positioned within one or more transverse hole(s) on the tube 952 andinto corresponding apertures 968 on the tip 958. The tip 958 comprises astop such as an annular flange structure 970 which abuts the distal endof the tube 952 and which supports the position of the allograft duringinsertion.

The tip 958 comprises a distal opening 960, a proximal opening 962, andan inner lumen 964 that is in communication with the tube lumen 955. Thetip 958 comprises threads 966 or other engagement structure to engagewith the allograft being inserted into the treatment site.

It will be understood that any of the material inserters describedherein can be used with any suitable material(s), depending on theparticular type of treatment procedure and treatment site. For example,any one the material inserters described above (e.g., 600, 640, and 950)can be used for the delivery of augmentation materials (e.g., ahydrogel) to a treatment site (e.g., a disc space), thereby making thematerial inserter an augmentation material inserter.

In accordance with one aspect of the embodiments described herein, thereis provided an exchange system providing a protected portal to thetreatment site (e.g., the sacrum) for the insertion of instrumentationor implants having O.D. dimensions (e.g., greater than about 0.35″) thatare too large to be accommodated through the working and docking portalprovided by the large dilator sheath (e.g., sheath 220 described above).

With reference to FIGS. 26-27 and 28A-B, in one embodiment, the exchangesystem assembly comprises an exchange bushing 702 and an exchangecannula 704.

The shaped exchange bushing 702 extends between a distal end 710 and aproximal end 712. The elongate, cannulated exchange bushing 702 isshaped and tapered toward its distal end 710. In one embodiment, thebushing 702 is cannulated with a central lumen having an inner diameterof about 0.14″ (i.e., slightly larger than a diameter of a typical guidepin). In one embodiment, the length of the bushing 702 is approximately14.00″.

Bushing 702 has a tapered tip 714 at its distal end 710. In oneembodiment, the tapered tip 714 starts at the inner diameter of thebushing 702 and continues at approximately an 18 degree angle for about0.5″ after which the taper cuts sharply back (i.e., flares out) towardsthe center of the bushing 702 and begins the taper again at about an 18degree angle out to the outer diameter of the bushing 702. This createsan annular recess region in which the exchange fingers 724 of thecannula 704 can nest, thereby providing a protected profile duringdelivery (i.e., the bushing 702 protects the exchange fingers 724) SeeFIG. 27. Delivery may be accomplished over an extended guide pin.

In one embodiment, the exchange bushing 702 comprises a polymericmaterial, such as an acetal copolymer or the like. In another embodimentthe exchange bushing 702 is fabricated from a metal or metal alloy,e.g., stainless steel. The exchange bushing 702 can be either machinedor injection molded.

With reference to the embodiments in FIGS. 27 and 28A-B, there isprovided an exchange system that comprises a “fingered” exchange cannula704, which works in combination with the bushing 702. The exchangecannula 704 extends between a distal end 720 and a proximal end 722 anddefines an inner lumen 728.

The exchange cannula 704 comprises a plurality of distally extending“fingers” 724 at the distal end 720 that are generally triangular inshape. FIG. 28A shows the exchange cannula 704 in the “open” positionwith its fingers 724 extended radially outward compared to the “closed”position. FIG. 28B shows the exchange cannula 704 in the “closed” orinsertion position with its fingers 724 congregated about a centralaxis, thereby forming a conical tip 726. The conical tip 726 is designedto enter the sacral bore, and to hold dilation and position intactduring subsequent deployment of instrumentation or implants.

In one embodiment, the exchange cannula 704 is formed from polymerictubing (e.g., such as acetal copolymer) In one embodiment, the cannula704 is about 8.00″ in length, and comprises from 3 to 8 “fingers” 724 atthe distal end 720 that are approximately triangular in shape. Here, thefingers 724 are approximately 1.00″ in length and configured so as tocollapse towards the longitudinal axis of the cannula at approximately a30 degree angle.

In one mode of use, the exchange cannula 704 is seated on the outside ofthe shaped exchange bushing 702 during insertion into the sacrumfollowing removal of the large dilator sheath 220 (i.e., working cannulathat was used for cutting and extraction). Once the shaped exchangebushing 702 is seated in the sacrum, the exchange cannula 704 isadvanced distally and into place. The fingers 724 of the exchangecannula 704 slip into the hole or entry point leading to the treatmentsite, and the shaped exchange bushing 702 is withdrawn enabling theinsertion of subsequent instrumentation or other devices and implantsthrough the lumen 728 of the exchange cannula 704 and into the treatmentsite. In one approach, the subsequent instruments can optionally beadvanced through the cannula 704 in combination with a guide pin.

With reference to FIGS. 29A-B, the largest O.D. of the to-be-deployeddevice 800 (i.e., the O.D. toward the proximal end of the device 800)exceeds that of the dilator sheath 220 and that of the exchange cannula704 while in its “closed” configuration. The device 800 is subsequentlydelivered to the treatment site by radially outwardly displacing thefingers 724 of the exchange cannula 704 to create a pathway that has adiameter large enough to accommodate the passage of the device 800,while isolating the working channel from adjacent organs or anatomicalstructures.

In accordance with another aspect of the embodiments described herein,there is provided an exchange system that provides a protected a portalto a treatment site, and that comprises an exchange bushing and anexchange tube. With reference to FIGS. 30A-C, in one embodiment, thereis provided exchange system assembly 730 comprising an exchange bushing732 and an exchange cannula 734.

The exchange bushing 732 comprises a tube 740 that extends between adistal end 742 and a proximal end 744, and defines an inner lumen 741.The bushing distal end 742 is typically beveled at an angle of about 20°to about 70°, often about 30° to about 60°. In one embodiment, thedistal end is beveled at an angle of about 45°. The outside diameter mayalso be tapered to a reduced diameter at the distal end 742 tofacilitate advance through the tissue tract.

The bushing 732 is typically machined or injection molded from stainlesssteel, delrin etc. or any other known suitable material.

The exchange cannula 734 comprises a tube 750 that extends between adistal end 752 and a proximal end 754, and defining an inner lumen 751.The tube distal end 752 is typically beveled at an angle of about 20° toabout 70°, often about 30° to about 60°. In one embodiment, the distalend 752 is beveled at an angle of about 45°.

The exchange cannula 734 is typically formed from stainless steel, orfrom a suitable polymer, such as acetal copolymer, or the like.

With reference to the exchange assembly 730 shown in FIG. 30A, thedistal portion of the exchange bushing 732 protrudes from distal end 752of the exchange tube 734. In one mode of use, the bushing 732 isdistally advanced into the sacrum over the dilator sheath 220 describedabove. Once the bushing 732 is advanced over the sheath 200 and seatedon the sacrum, the exchange cannula 734 is distally advanced over thebushing 732 and into place. The bushing 732 is then withdrawn over thedilator sheath 220, which is then also removed, enabling the insertionof subsequent instruments, devices, or implants through the lumen 751 ofthe tube 734. In one embodiment, the subsequent instruments, devices, orimplants are advanced through the lumen 751 over a guidewire. In anotherembodiment, the subsequent instruments, devices, or implants areadvanced through the lumen 751 without the aid of a guidewire.

With reference to FIGS. 30D-E, in a preferred embodiment, the exchangesystem 730′ comprises a bushing 732 and an exchange cannula 734′. Theexchange cannula 734′ comprises a handle such as an annular band 756 atthe proximal end 754′. The annular band 756 or other aspect of proximalend 744 comprises one or more indicium such as lines, pins or notches768, 769, as orientation indicators to show the rotational alignment ofthe bevel of the distal end 752′ of the exchange cannula 734′.

In accordance with one aspect of the embodiments described herein, thereis provided a temporary distraction device for separating adjacentvertebral bodies. In one mode of use, the temporary distraction tool isused for preparation of a disc space for receipt of augmentationmaterials (e.g., osteogenic materials, or annulus repair or sealantmaterials). In another mode of use, the temporary distraction tool isused to prepare a disc space for subsequent soft fusion (e.g.,osteogenic, osteoconductive, or osteoinductive procedure without afusion rod). In another mode of use, the temporary distraction tool isused to accommodate subsequent implantation of fusion or motionpreservation devices. Background information on distraction devices ingeneral appears in co-pending U.S. patent application Ser. No.10/309,416, filed on Dec. 3, 2002, the content of which is incorporatedin its entirety into this disclosure by reference.

In an application where only temporary distraction is desired, atemporary distraction device should be able to cause a separation of theadjacent vertebral bodies, and thereafter be removed without causingcompression of the intervening disc. This is accomplished in accordancewith the present invention by providing a temporary distraction workingtip on a temporary distraction tool which is similar to the distractionimplant 800 previously described. However, by providing the device intwo pieces as described below, the structure may be utilized to achievedistraction by rotation in a first direction, and the device maythereafter be removed from the patient without causing compression.

In accordance with one aspect of the embodiments described herein, thereis provided a two-piece temporary distraction device for achievingseparation of adjacent vertebral bodies, while permitting removal of thedevice without recompressing the intervening disc space. In oneembodiment, shown in FIGS. 31, 32A-B and 33A-E, the two-piece temporarydistraction device 860 comprises a distal piece 862 and a proximal piece864.

The distal and proximal pieces 862 and 864 comprise screw externalthreads 863 and 865, respectively. The thread pitches of the externalthreads 863 and 865 are chosen to achieve the desired or targeted levelof distraction, as explained in further detail in co-pending andcommonly assigned U.S. patent application Ser. No. 10/309,416 filed onDec. 3, 2002, which is incorporated herein in its entirety by reference.

With reference to FIGS. 33A-B, the distal piece 862 extends between adistal end 872 and a proximal end 874 and has external threading 863along at least a portion of its longitudinal axis. The proximal end 874of the distal piece 862 comprises an external non-threaded segment 875.In the present embodiment, non-threaded segment 875 comprises the maleportion of a lap joint that engages female portion 885 of proximal piece864, as described in further detail below.

The external threading 863 typically has a pitch of about 10 to about 16threads per inch, often about 10 to about 14 threads per inch. Theexternal threading 863 typically has a major diameter of about 0.350″ toabout 0.550″, often about 0.400″ to about 0.500″. The external threading863 typically has a minor diameter of about 0.230″ to about 0.490″,often about 0.280″ to about 0.380″. In one embodiment, the externalthreading 863 on distal piece 862 extends about 1.00″ along thelongitudinal axis of the distal piece 862.

The distal piece 862 comprises a cavity 877 defined by an internalunthreaded segment 878 and an internal threaded segment 879. Thedimensions of segments 878 and 879 are chosen to facilitate temporaryengagement with the insertion tip 900 of the insertion assembly 901, aswell as temporary engagement with the extraction tip 920 of theextraction assembly 921, as described in further detail below.

Internal segment 878 is typically non-circular in cross-section. Forexample, in the present embodiment, the segment 878 comprises arectangular cross-section. In another embodiment, not illustrated, thesegment 878 comprises a hexagonal or other polygon or non circularcross-section. In general, cross-sectional shape of the segment 878 iscomplementary to the shape or geometry of segment 910 of the insertiontip 900 of the insertion assembly 901, described in further detailbelow, to allow torque transmission from the insertion assembly 901 tothe distal piece 862.

Internal threaded segment 879 comprises internal threading 880 that iscomplementary to external threading 930 on the extraction tip 920 of theextraction assembly 921, described in further detail below. The portionof the cavity 877 defined by the segment 879 typically has a largerdiameter than that defined by the segment 878.

The length of the distal piece 862 is typically in the range of about0.5″ to about 2.00″, often about 1.00″ to about 1.25″. In one exemplaryembodiment, the length of the distal piece 862 is approximately 1.125″.

The actual dimensions (e.g, length, inner diameter, outer diameter,etc.) of the distal piece 862, proximal piece 864, device 860, etc.described herein will depend in part on the nature of the treatmentprocedure and the physical characteristics of the patient, as well asthe construction materials and intended functionality, as will beapparent to those of skill in the art.

With reference to FIGS. 33C-E, the proximal piece 864 extends between adistal end 882 and a proximal end 884 and has external threading 865along a portion of its longitudinal axis. The distal end 882 of theproximal piece 864 comprises an internal non-threaded segment 885 In thepresent embodiment, non-threaded segment 885 comprises the femaleportion of a lap joint that engages male portion 875 of distal piece862.

The proximal piece 864 comprises a cavity 887 defined by internalunthreaded segment 888 and internal threaded segment 889. The dimensionsof segments 888 and 889 are chosen to facilitate temporary engagementwith the insertion tip 900 of the insertion assembly 901, as well astemporary engagement with the extraction tip 920 of the extractionassembly 921, as described in further detail below.

As with internal segment 878 described above, internal segment 888 istypically non-circular in cross-section. For example, in the presentembodiment, the segment 888 comprises a polygon such as a rectangularcross-section. The cross-sectional shape of the segment 888 iscomplementary to the cross-sectional shape of segment 910 of theinsertion tip 900 of the insertion assembly 901.

As with internal threaded segment 879 described above, internal threadedsegment 889 comprises internal threading 890 that is complementary tothe external threading 930 on the extraction tip 920 of the extractionassembly 921. The portion of the cavity 887 defined by the segment 889typically has a larger diameter than that defined by the segment 888.

The length of the proximal piece 864 is typically in the range of about0.5″ to about 1.75″, often about 0.75″ to about 1.25″. In one exemplaryembodiment, the length of the proximal piece 864 is approximately 1.00″.

The outer diameter (O.D.; i.e., the major thread diameter) of theproximal piece 864 is typically in the range of about 0.40″ to about0.70″, often about 0.5″ to about 0.6″. In one exemplary embodiment, theO.D. of the proximal piece 864 is approximately 0.550″.

The threading 865 typically has a pitch of about 8 to about 12 threadsper inch, often about 9 to about 11 threads per inch. The threading 865typically has a minor diameter of about 0.240″ to about 0.620″, oftenabout 0.380″ to about 0.480″.

In one embodiment, internal threaded segment 889 has a length of about0.375″ along the longitudinal axis. In one embodiment, the internalunthreaded segment 888 has a length of about 0.625″ along thelongitudinal axis.

In one embodiment, the distal piece 862 and proximal piece 864 of thetemporary distraction device 860 are positioned relative to each otherby engaging the male portion of lap joint 875 with the female portion885.

The length of the assembled device 860 is typically in the range ofabout 1.50″ to about 2.50″, often about 1.90″ to about 2.10″. In oneexemplary embodiment, the length of the device 860 is approximately2.00″.

The distal and proximal pieces 862, 864 are typically made from anyknown suitable material, such as, for example, stainless steel,titanium, aluminum, or the like, or composites thereof.

In accordance with one aspect of the embodiments described herein, thereis provided an insertion assembly for delivering a two-piece temporarydistraction device into the treatment site.

In one embodiment, shown in FIGS. 32A and 34A-C, the assembly 901comprises a two-piece temporary distraction device 860, an insertion tip900, and a driver tool 855.

With reference to FIGS. 34A-C, the insertion tip 900 extends between adistal end 902 and a proximal end 904 and comprises a distally-locatedsegment 910 that is designed to releasably engage with internal segments878 and 888 of the two-piece device 860. In the present exemplaryembodiment, the segment 910 comprises a rectangular structure. Inanother embodiment, not illustrated, the segment 910 comprises ahexagonal, or other noncircular longitudinally extending structure.

The insertion tip 900 comprises a proximally-located segment 915 that isshaped and dimensioned to engage with the driver tool 855, described infurther detail below. In the present exemplary embodiment, the segment915 comprises a hexagonal cross-section. In another embodiment, thesegment 915 comprises an octagonal or other non-circular longitudinallyextending structure.

The insertion tip 900 may also be provided with one or more attachmentstructures such as holes or recesses 917 positioned to align withcorresponding structure such as hole(s) 859 of the driver tool 855 toreceive one or more screws or pins 854 to secure the tip 900 into thedriver tool 855.

The length of the segment 910, is typically in the range of about 0.50″to about 1.50″, often about 0.90″ to about 1.10″. In one exemplaryembodiment, the length of the insertion tip 900 is approximately 1.00″.

The insertion tip 900 is typically made from any known suitablematerial, such as, for example, stainless steel (e.g., 17-4 alloy),titanium, or the like, or composites thereof.

With reference to FIGS. 31, 32A and 34A-C, the driver tool 855 comprisesa shaft 899 that extends between a distal end 856 and a proximal end857. The tool 855 comprises a proximally-located handle 858 and one ormore distally-located holes 859 positioned to align with the hole(s) 917of the insertion tip 900 (described above) or the extraction tip 920(described below), and to receive one or more screws or pins 854 tosecure tips 900 or 920 into the tool 855.

The distal end 856 of the driver tool 855 comprises an aperture 850 forreceiving the proximally-located segments 915 and 935 of the tips 900and 920, respectively. In general, the cross-sectional shape andlongitudinal length of the aperture 850 is complementary to that ofsegments 915 and 935. For example, in the illustrated embodiment, boththe aperture 850 and segments 915 and 935 comprise a hexagonalcross-section and have a length of about 0.375″.

The overall length of the driver tool 855 is typically in the range ofabout 12.00″ to about 16.00″, often about 13.00″ to about 15.00″. In oneexemplary embodiment, the length of the driver tool 855 is approximately14.00″.

The outer diameter (O.D.) of the driver tool 855 is typically in therange of about 0.25″ to about 0.50″, often about 0.35″ to about 0.40″.In one exemplary embodiment, the O.D. of the driver tool 855 isapproximately 0.375″.

The driver tool 855 and its component parts are typically made from anyknown suitable material, such as, for example, stainless steel,titanium, aluminum, or the like, or composites thereof. The handle 858is typically welded over the proximal end 857 of the tool 855.

In accordance with one aspect of the embodiments described herein, thereis provided an extraction assembly for removing a temporary distractiondevice without causing compression across the intervening disc space.

In one embodiment, shown in FIGS. 32B and 35A-C, the assembly 921comprises a two-piece temporary distraction device 860, an extractiontip 920, and a driver tool 855.

With reference to FIGS. 35A-C, in one embodiment, the extraction tip 920extends between a distal end 922 and a proximal end 924 and comprises adistally-located threaded segment 931 that is designed to releasablyengage with the receiving segments 879 and 889 of the distal piece 862and proximal piece 864, respectively of the distraction device 860.

In one embodiment, the distally-located threaded segment 931 of theextraction tip 920 comprises left-handed external threads 930 thatcomplement left-handed internal threads 880 and 890 of the receivingsegments 879 and 889, respectively. The left-handedness of the threads880, 890, 930 make it possible to rotate the extraction tool assembly921 in a counter-clockwise direction, to engage each piece 862 and piece864, and remove or extract each of them sequentially, proximal 864first, from the treatment site while rotating the assembly 921 in thecounter-clockwise direction to unscrew each of the pieces of thedistraction device 860 from the bone.

The extraction tip 920 comprises a proximally-located attachment surfaceon segment 935 that is shaped and dimensioned to releasably engage witha corresponding surface on driver tool 855. In the present exemplaryembodiment, the segment 935 comprises a hexagonal cross-section. Inanother embodiment, not illustrated, the segment 935 comprises anoctagonal cross-section or other non-circular longitudinally extendingstructure.

The extraction tip 920 also comprises a releasable engagement structuresuch as one or more holes 937 positioned to align with hole(s) 859 ofthe driver tool 855 and receive one or more screws or pins 854 to securethe tip 920 into the driver tool 855. Preferably, the components of thesystem are configured such that the same driver tool 855 can be used toextract both the proximal piece 864 and distal piece 862 from thetreatment site.

The length of the extraction tip 920 is typically in the range of about0.50° to about 1.50″, often about 0.90″ to about 1.10″. In one exemplaryembodiment, the length of the extraction tip 920 is approximately 1.00″.The extraction tip 920 is typically made from any known suitablematerial, such as, for example, stainless steel, titanium, or the like,or composites thereof.

In accordance with one aspect of the modes of use described herein,there are provided methods of using a two-piece distraction device totemporarily separate two or more vertebral bodies in the spine.

In one mode of use, for a two vertebral body application, the two-piecetemporary distraction device 860 is introduced into the treatment siteby advancing segment 910 of the insertion tip 900 coaxially intoengagement with internal segments 878 and 888 of the device 860, andthen rotating the device 860 into an axial bore as described elsewhereherein, under force applied generally distally. In one typicalapplication, the device 860 is used to cause the separation of twoadjacent vertebral bodies along the AAIIL. The device 860 is advancedthrough a caudal, proximal vertebral body, through an intervertebraldisc, and into a cephalad, distal vertebral body, thereby causingdistraction of the cephalad and caudal vertebral bodies, relative toeach other. Rotation is continued until the desired degree ofdistraction has been achieved, as may be evaluated using conventionalimaging technology. Over distraction can be corrected by rotating thedistraction device 860 in an opposite direction.

Once the desired distraction has been achieved, the device 860 may beremoved from the treatment site piece-by-piece by sequentially removingthe proximal piece 864 and the distal piece 862 in a proximal direction.Following proximal retraction of the insertion tool, segment 931 of theextraction tip 920 is distally advanced to and rotatably engaged withthe internal segment 889 of the proximal piece 864, and then rotated ina predetermined direction to cause disengaged of the proximal piece 864from the distal piece 862, and thereby facilitating removal of theproximal piece 864 from the treatment site. The segment 931 is thenreadvanced distally through the access bore and engaged with theinternal segment 879 of the distal piece 862, and then rotated in apredetermined direction to cause of the distal piece 862 to be extractedfrom the treatment site.

In one mode of use, the above-described two-piece device 860 andassemblies 901 and 921 are used to achieve temporary distraction (i.e.,restoration of disc height) in preparation for implantation of either afusion or a mobility restoration or preservation device as noted above.In one approach, distraction is maintained following removal of thedistraction device 860 and before implantation of the therapeuticimplant by having the patient lie in a prone or flat position on ahorizontal surface, thereby relieving the patient's spine of axialcompressive forces resulting from load bearing, motion, and the effectsof gravity. In a fusion application, an implantable distraction deviceor other fusion implant may be supplemented by subsequent posteriorinsertion of facet or pedicle screws.

Various combinations of the tools and devices described above may beprovided in the form of kits, so that all of the tools desirable forperforming a particular procedure will be available in a single package.Kits in accordance with the present invention may include access kits,such as for achieving percutaneous access to the sacrum, and access kitsfor achieving soft tissue access to the sacrum and access through thesacrum into the desired treatment zone. Kits may also be provided withthe tools necessary for disc preparation. Further kits may be providedwith temporary distraction and/or insertion tools for insertion ofimplants.

Access kits may include all or any sub-combination of the followingcomponents, which have been described previously herein: one or moreguide pin introducers, stylet, guide pin, guide pin handle, and guidepin extension. Each of these components may be either reusuable ordisposable. The access kit may additionally include one or moredilators, such as a 6 mm dilator and 8 mm dilator, and a 10 mm dilatorwith sheath. In one implementation of the kit, each of the dilators isreusable, and the sheath is disposable. The access kit may additionallyinclude twist drills, such as a 6 mm, 7.5 mm and 9 mm drills which maybe reusable.

Disc preparation kits may differ, depending upon whether the procedureis intended to be one level or multi-level. The disc preparation kit mayinclude a plurality of cutters. In a single level kit, anywhere from 3to 7 cutters and, in one embodiment, 5 cutters are provided. In a twolevel kit, anywhere from 5 to 14 cutters may be provided, and, in oneembodiment, 10 cutters are provided. All of the cutters may be one timeuse disposable.

The disc preparation kit may additionally include one or more tissueextraction tools, for removing fragments of the nucleus. In a one levelkit, 3 to 8 tissue extraction tools, and, in one embodiment, 6 tissueextraction tools are provided. In a two level disc preparation kit,anywhere from about to 8 to about 14 tissue extraction tools, and, inone embodiment, 12 tissue extraction tools are provided. The tissueextraction tools may be disposable.

The disc preparation kit may additionally include a bone graft inserter,which may be disposable.

An allograft kit may be provided including, in addition to the tools inthe access and disc preparation kits, an allograft inserter tool and atemporary distraction tool. A selection of twist drills may be provided,such as a 9.5 mm, 10 mm, 10.5 mm, 11 mm or 11.5 mm twist drill,depending upon the size of the desired graft. The allograft kit mayadditionally include an exchange system, including a cannula andbushing, as have been described previously herein.

A fusion kit intended for a one level fusion may include, in addition tothe tools in the access and disc preparation with bone graft inserterkits a one piece fusion rod, a rod driver, and a paste inserter. Thefusion kit may additionally include a plug, a plug driver, and one ormore twist drills such as a 7.5 mm and a 6 mm. The fusion kit willadditionally include an exchange system as has been discussed. The roddriver and twist drills may be reusable.

In an alternate fusion kit, intended for two-level fusion, the kit mayinclude one, two-pieces fusion rods, or one, one-piece fusion rod andone mobility implant, or a two-piece implant, one of which is a fusionimplant and one of which is a mobility device The fusion kitadditionally includes a rod driver, a paste inserter, one proximal andone distal plugs and two plug drivers. The fusion kit may additionallyinclude one or more twist drills, such as a 7.5 mm and a 6 mm twistdrill. The fusion kit will additionally include an exchange system.

Although the present invention has been described in terms of certainpreferred structures and embodiments, variations on the foregoing willbecome apparent to those of skill in art in view of the disclosureherein, and are considered to be within the scope of the presentinvention. Accordingly, the present invention is not intended to belimited by any of the forgoing disclosure, and is instead intended toextend to the full scope of the following claims.

1. An exchange system for increasing the cross sectional area of anaccess pathway through soft tissue to a surface of a bone, comprising:an elongate, tubular exchange bushing, having a proximal end, a distalend and a central lumen extending therethrough; and an elongate, tubularexchange cannula, having a proximal end, a distal end and a centrallumen extending therethrough, the exchange cannula comprising a beveleddistal end; wherein the exchange bushing is axially slidable within thecentral lumen of the exchange cannula.
 2. An exchange system as in claim1, wherein the bevel is at an angle within the range of from about 20degrees to about 70 degrees with respect to a longitudinal axis of theexchange cannula.
 3. An exchange system as in claim 2, wherein the bevelis at an angle within the range of from about 30 degrees to about 60degrees with respect to the longitudinal axis of the exchange cannula.4. An exchange system as in claim 1, further comprising a handle on theproximal end of the exchange cannula.
 5. An exchange system as in claim4, wherein the handle comprises an annular band.
 6. An exchange systemas in claim 1, further comprising an indicium of the rotationalorientation of the bevel.
 7. An exchange system as in claim 6, whereinthe indicium comprises a visible marker on the proximal end of theexchange cannula.
 8. An exchange system as in claim 7, wherein theindicium comprises at least one notch on an annular band carried by theproximal end of the exchange cannula.
 9. An exchange system as in claim1, further comprising a plurality of distally extending fingers on thedistal end of the exchange cannula, the fingers movable between a first,reduced outside diameter configuration and a second, enlarged outsidediameter configuration.
 10. An exchange system as in claim 9, whereinthe exchange bushing comprises a recess for receiving the fingers whenin the first, reduced outside diameter.
 11. A method of advancing adevice along an access tract, comprising the steps of: positioning adilator sheath between an access site and a target site on a bone;advancing a tubular exchange bushing over the dilator sheath; advancinga tubular exchange cannula over the exchange bushing; removing thedilator sheath and the exchange bushing, leaving the exchange cannula inposition along the access tract; and introducing the device through theexchange cannula.
 12. A method as in claim 11, wherein the device is animplant.
 13. A method as in claim 11, wherein the device is a spinalfusion implant.
 14. A method as in claim 11, wherein the device is aspinal motion preservation implant.
 15. A method as in claim 11, whereinthe device is a site preparation tool.
 16. A method as in claim 11,wherein the device has a cross sectional area that is greater than theinside cross sectional area of the dilator sheath.
 17. A method as inclaim 11, wherein the target site is on the sacrum.
 18. A method as inclaim 11, wherein the introducing the device step comprises enlargingthe diameter of at least a portion of the exchange cannula.
 19. A methodas in claim 18, comprising radially enlarging a distal tapered portionof the exchange cannula.
 20. A method as in claim 11, wherein the accesstract has a longitudinal axis which intersects the surface of the boneat an angle, and the distal end of the exchange cannula is beveled at anangle that corresponds to the angle at which the axis intersects thesurface of the bone.